Following Liverpool's victory at Stamford Bridge earlier this afternoon, and United's failure to beat Everton, Arsene Wenger's side knew just what was at stake as they looked to keep pace with the Barclays Premier League leaders.
The Gunners - fresh from a fine 5-2 Champions League trashing of Fenerbahce in Turkey - certainly had to dig deep for their win, which came courtesy of an own goal from Julien Faubert when he deflected a shot from substitute Emmanuel Adebayor late in the second half, which was harsh on inspired West Ham keeper Robert Green, before the African wrapped things up in stoppage time.
Nevertheless, it is these such keenly-contested clashes which Wenger's young squad will have to come through if they are to have a say in the destiny of the title come May - and on this afternoon's evidence, they could still just have the final word.
Arsenal were led once more by captain William Gallas, fit again following a thigh problem.
However, both he and fellow France veteran Mikael Silvestre were given plenty to concern themselves during the opening stages by a busy West Ham frontline.
After 10 minutes, it needed a fine tip over from Manuel Almunia to deny the lively David di Michele, who powered in a 20-yard drive which looked set for the top right-hand corner.
Arsenal were being out-manoeuvred in midfield, were Alexander Song, pushed forwards from defence, and Spanish maestro Cesc Fabregas were yet to strike up an understanding.
Winger Theo Walcott had been anonymous, but burst into the game on 20 minutes.
The England man turned his marker just inside the West Ham half before scampering away towards goal down the right.
After riding two challenges on the edge of the box, he darted inside and unleashed a fierce drive which cannoned off the top of Green's crossbar.
Although both Robin van Persie and Nicklas Bendtner were both well placed in the middle, given his current form, Walcott could perhaps be forgiven for being somewhat selfish.
The all-action teenager was in the thick of things again when an intelligent chest down from Van Persie 12 yards out put the ball into his path. However, despite getting a shot away, Green somehow pulled off a superb reflex save down to his right.
West Ham - who were out to avoid a third straight league defeat - needed something to relieve the pressure as the half-hour mark approached.
It came following a quick break when Craig Bellamy chased down a long ball ahead of Silvestre.
The Wales striker drilled in a low, first-time effort from the edge of the penalty area - which Almunia deflected over with his legs.
Bendtner chased what looked a lost cause on the left, before cutting inside to force another fine save from Green at full stretch.
After a low-key start to the second half, the visitors again maintained a spell of patient build-up.
It was almost rewarded when Samir Nasri picked out Walcott on the right, and his low centre was put up over his own bar by the back-tracking James Collins.
The West Ham defender then made a timely intervention to out-muscle van Persie as the Dutchman looked to get on the end of a long ball into the penalty area.
As the hour mark passed, Bellamy got in down the West Ham left - but Gallas was on hand to scramble the loose ball away.
Arsenal went close again when first Collins blocked Walcott's angled effort and then Van Persie's follow-up flew through a crowded six-yard box and hit Lee Bowyer.
With 25 minutes left, Wenger made a double change as Adebayor and Abou Diaby - who had played so well in Turkey - were introduced, replacing Nasri and Walcott.
Green was having an inspired afternoon and made another fine one-handed save to keep out Van Persie's low, angled drive.
When the England stopper was finally beaten by a stinging 25-yard free-kick from the Dutchman, his luck held as the ball cannoned off the base of the post and bounced away.
Arsenal, though, finally got the breakthrough with quarter of an hour to go when Adebayor weaved his way into the area and hit a low shot back across goal.
With Bendtner lurking in the six-yard box, the unfortunate Faubert stuck out a boot which diverted the ball past Green.
Adebayor should then have done better when following up his own shot, only to stab over from close range.
The Togo frontman eventually made sure of what could yet prove to be three vital points in an intriguing title race when he latched on to a long pass up field from Bendtner to round Green and smash the ball into an empty net.
To compound the misery for West Ham, referee Phil Dowd showed striker Carlton Cole what seemed a somewhat harsh straight red card for a sliding tackle from behind on Song.
"It was a big win for us today,'' Wenger said. "To come out of it with a frustrating 0-0 would have felt like a wasted opportunity to get closer to the top. We knew before the game we could not drop points today.
"West Ham can also feel frustrated because they defended well and gave everything today. Green always has the game of his life against us, it is unbelievable and he repeats that every year.
"We had some strikers on the bench and in the end that made the difference when we got some openings as they fatigued in the last 20 minutes.''
Wenger revealed he had taken a conscious decision to give Adebayor, who was last season's leading scorer, a rest.
"Last year I over-used him and now we go into a period where we play every three days, which is why I want to rotate a little bit," said Wenger. I have a short squad, a compact one, but of quality. I can only show that by trusting the players.''
Adebayor was a target for AC Milan during the summer, but eventually decided to stay at the Emirates Stadium. Wenger feels the Togo striker is showing his commitment to the Gunners cause.
He said: "He fights very hard and came on with 25 minutes left, and fought for every ball - that shows more than all the speeches I can make. We have a great spirit in the side, great quality and are very determined to come back to the top.''
Arsenal are now four points off leaders Liverpool, and have closed the gap on Chelsea to just one. Wenger feels this season will be "tight''.
He said: "One week ago everyone made Chelsea super-favourites, now it is Liverpool. Things change very quickly, which is why it makes it very interesting. We were very close last year and with 83 points, many times you would have been champions.
"However, Manchester United had a fantastic second half of the season, we dropped a little bit of our quality and that is it - I still feel any weakness will be punished.''
Emmanuel Adebayor and Theo Walcott put the Gunners 2-0 up inside 11 minutes and although Mikael Silvestre's own goal reduced the deficit, Abou Diaby restored the Gunners' cushion.
Four minutes after half-time Alex Song volleyed in a fourth to extend the Gunners' lead at the top of the group.
The profligate Daniel Guiza pulled a goal back in the 77th minute but it was too late to affect the outcome and substitute Aaron Ramsey fired in off a post in the fourth minute of injury time.
It was the hosts' first defeat in Europe at home in 16 matches but in truth they were the architects of their own downfall.
Both teams defended poorly and the only difference between the two was up front where Arsenal took their chances and Fenerbahce did not.
Spain striker Guiza was the main culprit, squandering two excellent opportunities just before half-time which could have made it 3-3 at the interval and a much different proposition for Arsene Wenger's side.
In only the fourth minute Gunners goalkeeper Manuel Almunia, captain for the night, made the first save, rushing out to block Ugur Boral's close-range shot from Claudio Maldonado's right-wing cross.
The famous Fenerbahce atmosphere was evident from the start with every Arsenal attack greeted with a cacophony of boos and whistles.
But the crowd were silenced in the 10th minute when Adebayor beat the offside trap to collect Cesc Fabregas' through-ball and coolly slot past Volkan Demirel for his third Champions League goal in as many matches.
A minute later it was 2-0 as Fabregas replicated his defence-splitting pass and Walcott rounded the goalkeeper, who got half a touch, before firing inside the near post.
Had Samir Nasri had the confidence to hit Emmanuel Eboue's right-wing cross first time with his left foot three minutes later it would have been a third but he cut it back on to his right at the far post and Volkan saved.
Fenerbahce should have pulled one back immediately when Guiza's shot was half-blocked by Gael Clichy and it fell to Semih Senturk, who fluffed his kick from just five yards.
However, the hosts were gifted a goal in the 19th minute when Alex floated in a free-kick and Guiza volleyed across the six-yard area where Silvestre stuck out a leg and diverted the ball past Almunia.
Within two minutes Arsenal restored their two-goal cushion when a long ball forward picked out Diaby, who held off the challenge of two defenders to fire left-footed across Volkan and into the far corner of the net.
The tall midfielder was booked for pulling his shirt over his head but it could not dampen his delight at scoring.
In the 31st minute later Guiza volleyed past Almunia from close range from Gokhan Gonul's pass but it was ruled out for offside.
The Spain striker then twice raced clear but narrowly shot wide and then ran the ball straight into the goalkeeper when he should have done better on both occasions.
Arsenal took less than four minutes to extend their lead, and once again it came from some poor defending.
Fabregas' left-wing free-kick was not even half-headed away and when the ball dropped to Song on the edge of the six-yard area he lashed home a volley.
Fenerbahce tried to respond but they found the Arsenal defence less generous than had been the case in the first half.
Alex's superb pass picked out charging full-back Roberto Carlos but having controlled the ball with his left foot in the penalty area he could not hit it with his right and the chance was lost.
Guiza missed another chance when he again caught the defence square but shot straight at Almunia and then Edu's follow-up was cleared off the line Eboue.
With 17 minutes remaining Diaby was withdrawn and Ramsey sent on for his first proper taste of the Champions League having previously only played in the qualifying round.
In the 77th-minute Guiza finally atoned for his previous errors when he lobbed Alex's pass over Almunia but it appeared too little too late.
Seconds later he broke through again and fired at the goalkeeper, although he had already been flagged offside.
But in the fourth minute of injury time Ramsey fired in off a post to complete the rout.
Theo Walcott claimed Arsenal were "flying" after their emphatic 5-2 win over Fenerbahce in Istanbul tonight.
England hero Walcott scored the Gunners' second as Arsene Wenger's side maintained control of Champions League Group G.
Walcott told ITV: "It is a very difficult place to come, the fans get behind them but we all got our jobs right tonight and it was just a brilliant performance by everyone.
"Everyone is just flying. We are playing brilliant football and scoring plenty of goals from all sorts of positions.
"People are coming off the bench and scoring goals and it just shows how strong our squad is."
Wenger hailed the pace and technique of his side and felt their victory was fully deserved.
Emmanuel Adebayor, Abou Diaby, Alex Song and Aaron Ramsey also got on the scoresheet against the Turks.
Wenger told ITV4: ''I think it was a good game because Fenerbahce were dangerous as well.
''Overall I believe our mobility, our technique, our pace was superior and that made a big difference tonight.''
Wenger praised the performance of Diaby, who played in an advanced role.
''He can do it,'' the Frenchman said. ''He can play nearly everywhere, Diaby. From midfield going forward, he can play everywhere.
''He has been out for nearly three months now. It was his first start and he had a very good game.''
Wenger was also impressed by teenager Ramsey, his summer signing from Cardiff.
He said: ''He is 17 and a half years old, he is a very young boy but very promising. His personality really comes out wherever he goes. He really wants the ball, he is not frightened.
''We had a really young team out tonight, at 22 years old (average age), and it is good to see.''
Arsenal manager Arsene Wenger reflected on a job well done as his side hammered Fenerbahce 5-2 in the most open of Champions League matches in Istanbul.
Emmanuel Adebayor and Theo Walcott put the Gunners 2-0 up inside 11 minutes and although Mikael Silvestre's own goal reduced the deficit, Abou Diaby restored the Gunners' cushion.
Four minutes after half-time Alex Song volleyed in a fourth and although Spain striker Daniel Guiza pulled one back, substitute Aaron Ramsey completed the rout in injury-time.
It also allowed Arsenal to extend their lead at the top of Group G by a point after Dynamo Kiev won in Porto to move to into second, two behind the unbeaten Gunners.
With the defence down to bare bones and a five-man midfield, there were a number of questions Wenger's side had to answer in the volatile atmosphere of the Sukru Saracoglu Stadium.
The back four did not cover themselves in glory, allowing Spain striker Guiza too many chances which, on another day, would have brought him a hat-trick.
But the resting of forward Robin van Persie handed Diaby, who had been out since August with a thigh injury, a place in midfield and he showed his versatility by regularly getting forward and scoring the important third goal.
''I believe Diaby can be a player who can play between midfield and the strikers and has good penetrating power,'' said Wenger.
''I wanted to rest Van Persie because he played 90 minutes on Saturday for only the third time [this season] and I did not want to gamble.
''But Diaby would have played any way. It is the first game he has played for three months and he has responded remarkably well.''
Wenger also paid tribute to his team's attacking invention and desire - highlighted by Ramsey scoring in the fourth minute of injury-time when the Gunners should really have been looking to hold on to what they had.
Prior to last night Fenerbahce had not lost at home in Europe in 16 matches but they were torn to shreds in the opening 21 minutes.
''Because the two teams were going forward it was a very open game and Fenerbahce are an attacking side and are very dangerous going forward,'' said the Frenchman.
''The fact we scored an early goal forced Fenerbahce to come out and we caught them many times on the counter-attack.
''Our pace, movement and technique made the difference and allowed us to take advantage of it but it was not an easy game.
''I am very proud of the team. The average age was 23 and I am proud because we came in and tried to dictate the game in a very heated atmosphere.
''It is very pleasing that they seemed to play with no fear. I am pleased to see it works.
''We came here and had a go. We started strong, we remained quite strong and we finished strong.''
Arsenal manager Arsene Wenger has insisted that under-fire Tottenham Hotspur sporting director Damien Comolli is being made a "scapegoat" for the club's terrible start to the season.
With Spurs four points adrift at the bottom of the table following their worst ever start to the season, Comolli has been blamed for £70million worth of signings that have left the club without a win in eight league games.
The biggest question mark hangs over his dealings during this summer's transfer window when both Dimitar Berbatov and Robbie Keane departed the club with Roman Pavlyuchenko and Fraizer Campbell recruited as last minute replacements.
Comolli is widely expected to be sacked next week after Tottenham chairman Daniel Levy gave under-fire manager Juande Ramos a vote of confidence despite a 2-1 loss to newly promoted Stoke City at the weekend.
But Wenger, who recruited Comolli as one of his key European scouts at Arsenal before he headed to White Hart Lane, believes the finger of responsibility for Spurs' dire plight cannot be pointed at just one person.
Wenger said: "In every job there is always a culture of finding a scapegoat when things don't go well. We have to accept we're always guilty, even if not always responsible.
"In general you can only fight against that situation when you are united and I believe Damien is quality. I brought him here [to Arsenal] because I thought he was good.
"Tottenham, I think, has a good team, they have good players, and they will bounce back. The problem is when you are not doing well you are always attacked from the outside. What you can only do is to show a close, united attitude from inside to fight against that."
Asked if it was possible for the continental approach of a head coach working under a director responsible for recruiting players, rather than the unilateral managerial role Wenger enjoys at Arsenal, could work in England the Frenchman said: "I believe anything can work in football as long as the responsibilities are clear and accepted by everybody.
"In Tottenham's case I don't know how it works, but anything can work as long as people, when they sign their contracts, know clearly what their responsibilities are.
"You can't say now that the situation at Tottenham is down just to that. Football is a strange thing; when you lose confidence you can become quickly average, it is as simple as that."
Meanwhile, former Tottenham chairman Sir Alan Sugar has described the club's current predicament as ''a terrible situation'' but insists they should stand by manager Juande Ramos.
Sugar, who held a majority stake in Spurs from 1991 to 2001, told talkSPORT: ''Looking at the playing squad, in theory and on paper, there is no way we should go down.
''But you can never say never. It's a terrible situation at the moment; we just have to be patient. It's not like we don't have the players. We have a great squad. I keep saying it every game that it's got to come right.
''No-one is too big to go down. The table doesn't lie. You have to win games; it's as simple as that. Manchester United lose games on occasions. Arsenal lose games on occasions. Chelsea lose games on occasions. But we're losing them on too many occasions.
''It would be totally irresponsible at the moment to be talking in any terms about blaming any individuals, including the manager,'' Sugar added.
''The manager is no mug, he's achieved in the past. He's obviously a deep thinker and he's thinking about what he's got to do.''
Robin van Persie fires home the levellerArsene Wenger was forced to field a reshuffled defence because of injuries to captain William Gallas and Bacary Sagna, but the new-look back four was exposed after just nine minutes when Leon Osman put the visitors ahead.
However, after another enforced change when Kolo Toure was forced off at half-time because of a shoulder problem and England winger Theo Walcott was introduced from the bench, the team had better balance and soon drew level through Samir Nasri.
Robin van Persie - who on another day could have bagged himself a hat-trick - nodded in from close range to complete the comeback, with Walcott drilling home an angled effort in stoppage time to give the bruised Gunners renewed confidence for more stern challenges over the next seven months.
Arsenal were looking to improve on their last Premier League game here, when surprise package Hull pulled off a shock, but deserved, win.
But after what was a low-key start, Everton took an early lead.
The ball was knocked up field and dropped back to Osman. The midfielder played a pass out wide to Steven Pienaar on the left, continued his run into the area to meet the return cross and stabbed the ball past Manuel Almunia.
Arsenal - who had only lost two games since arriving at their new home in 2006 - were stunned into action, and soon lifted the tempo.
They should have been level when Van Persie beat the offside trap and collected a long pass from Fabregas into the area ahead of Joleon Lescott.
The Dutchman turned superbly, only for his shot to be blocked by a brilliant reaction save from American stopper Tim Howard.
In the 22nd minute, Arsenal defender Toure, captain in Gallas' absence, needed treatment for a shoulder problem after falling awkwardly at a corner.
Gael Clichy picked out Emmanuel Adebayor with a deep cross from the left, but the big African could not keep his header down.
Emmanuel Eboue then presented Van Persie with another great chance after a clever angled pass, only for the Dutchman to blaze the ball over from 20 yards.
After 30 minutes, Lescott pulled back Van Persie just outside the area on the right, and was cautioned.
The Holland forward took the free-kick himself, which Howard had to punch away double-fisted as it was whipped towards the far post.
With seven minutes to half-time, Everton went close again when Lescott's downward header from a Leighton Baines cross was cleared off the line by Clichy.
Fabregas flashed a 25-yard effort just wide of Howard's right-hand post and then from close range dragged a shot across goal to sum up a frustrating opening 45 minutes by the off-key Gunners.
Toure had been struggling and was unable to continue for the second half, with Alex Song moving from the right into the middle and Eboue dropping back as Walcott came on.
It was Almunia though who was called into action right away, as Ayegbeni Yakubu got on the end of a knockdown by Marouane Fellaini.
Arsenal, though, were soon pressing down on the Everton goal and drew level through Nasri on 48 minutes.
A corner was only half-cleared, with Denilson playing the ball back to the edge of the area, where Mikael Silvestre - making a belated debut after signing from Manchester United - touched it back to Nasri, who drilled a low strike past the defenders and an unsighted Howard.
Suddenly the Emirates Stadium faithful had found their voice again and the team responded with a number of free-flowing moves.
Van Persie blazed the ball over when it fell to him 12 yards out and then looked to have a strong penalty claim when he went down under a challenge from Baines - but the referee was having none of it.
Peter Walton was then centre stage once more when Tony Hibbert went in late on Denilson and was involved in some unnecessary afters with Clichy which saw a brief melee. The Northamptonshire official, though, decided a yellow card was sufficient punishment for both men.
Arsenal continued to press, but were confronted by a wall of blue shirts around the penalty area.
However, they finally found a way through on 70 minutes. Adebayor went into the left side of the box, before setting up Fabregas.
His strike was parried by Howard - and Van Persie was on hand to nod the ball in, despite the best efforts of Baines on the line.
Abou Diaby came on for his first appearance of the season to replace Nasri - and promptly set up Walcott to make it 3-1 in stoppage time.
GettyImagesThe Gunners head into tomorrow's clash against Everton at the Emirates Stadium without captain and centre-half William Gallas as well as full-back Bacary Sagna, who both picked up knocks while away with France.
Add to that the enforced absence of fellow defender Johan Djourou because of concussion and striker Nicklas Bendtner, who has an ankle problem, and suddenly Wenger's options - particularly at the back - appear somewhat depleted.
However, the Arsenal manager is confident enough that with the return of Abou Diaby for the first time this season following a thigh problem and midfielder Cesc Fabregas having pledged to play through the pain barrier after breaking his nose during the international break, he can even afford to give England winger Theo Walcott a rest.
The Gunners are also expected to give veteran Mikael Silvestre a belated debut following his transfer from Manchester United.
Wenger, though, is anything but complacent having seen his men already lose twice this season - the same amount as in the entire of their last league campaign when they again missed out on the title as both Manchester United and Chelsea overtook them during the run-in.
With two more points dropped at Sunderland in their last match before a fortnight off, Arsenal, currently in fourth place, cannot afford many more off days if they are to remain serious challengers over the next seven months.
"If you ask me how many games you think we can lose, I would say zero because I always start a season thinking you cannot lose a game, but we have lost two already and we are in a position where we have given ourselves a handicap,'' he said.
"However, I still think it is manageable to get back to the top and I want to lead this team knowing that there is not a lot of margin of error left - but I still think we can do that.''
Wenger hopes all of his latest players to head to the treatment room will be short-term, with winger Tomas Rosicky and striker Eduardo both continuing their long roads back to full match fitness.
Forward Robin van Persie has recovered from a muscular problem picked up while away with Holland, but Walcott could be given a breather tomorrow.
"Theo has come back available, but I might rest him because he played on Wednesday night in Minsk. We have that option,'' Wenger added.
Everton boss David Moyes has vowed to rebuild his squad if they are unable to re-capture the form of the past few years.
Everton have won just two games this season. They also lost a Merseyside derby and have been dumped out of the UEFA Cup and the Carling Cup.
Moyes - who earlier this week signed a new five-year contract - will tomorrow take an injury-hit squad to the Emirates, while the following weekend champions Manchester United are the visitors to Goodison Park.
The Blues are without Tim Cahill, who completes a three-match ban, whiles fellow midfielder Segundo Castillo picked up a hamstring strain on international duty with Ecuador, and defenders Phil Jagielka and Joseph Yobo have flu.
Striker Victor Anichebe and captain Phil Neville are also still recovering from hamstring problems. Leon Osman has a groin strain.
Moyes said: "I would one day like to be as stable as Arsenal and Manchester United. They are in a different situation regarding finance, but the stability has helped them.
"Did I think that we could have taken Everton into the Champions League, or the UEFA Cup regularly?
"Maybe I felt that might be a little beyond us, but we have managed it and done pretty well with what we have had.
"But if we do not get things back to what they were last season we will have to start working on re-assembling another team for years to come.''
He added: "The facts show that clubs who make regular changes end up in trouble, including financial trouble. Now we are not in financial trouble but we have trouble because we need another investor.
"We have never had much money, and that is the case at the moment. But everyone works really hard to get to the top.
"In the last few seasons we have given it a good go, and that is what we will do again.
"Apart from five or six managers in the country, the rest of us are unable to move our clubs on in the way we would want. "
Arsenal will be without William Gallas, Bacary Sagna and Nicklas Bendtner over the next week after all three sustained injuries while on international duty.
Manager Arsene Wenger today admitted his side had suffered "heavy losses'' with further concerns over three other players.
Gallas (hamstring), Sagna (knee) and Bendtner (ankle) will all miss this weekend's Barclays Premier League clash with Everton and next Tuesday's Champions League trip to Fenerbahce.
Cesc Fabregas (broken nose), Robin van Persie (muscular) and Johan Djourou (concussion) also suffered knocks but Wenger is hopeful they should be able to feature. Abou Diaby will also be included in the squad for the first time this season this weekend after overcoming a thigh problem.
Wenger told Arsenal TV Online: "Unfortunately we have lost some players over the 10 days - William Gallas, Bacary Sagna and Nicklas Bendtner. These are heavy losses and we have to compensate them.
"Fortunately the three of them don't look to be out for a long, long time but they will be out for the weekend game and I think the game on Tuesday.
"As well as them, Djourou got concussion during his game with Switzerland and will be assessed tomorrow to see if he is available. He does not look too bad and he could have a good chance to play.
"I am still waiting for Robin to come back so I don't know about him. However, he should be okay.
"He went with a muscle problem but he came on after 56 minutes last night and, from the reports I got, he should be all right. Both of them will be assessed.
"Also I am told Cesc has a broken nose. It should not stop him playing. He is here now and is being assessed.''
One way the losses will be compensated for will be in the return of Frenchman Diaby.
"At least Abou Diaby is back in the squad again,'' Wenger said. "Even though he has not played games he will be used, at the least in the squad, because we have lost those three players.''
Fabregas rescues Arsenal
