Arsenal closed the gap on Premier League leaders Liverpool to two points after an impressive second-half show cracked Nottingham Forest's resistance at the City Ground.
Gabriel Jesus' opener at the City Ground was his fourth in the Premier League so far this season.
The Gunners struggled to break down Forest's well-organised rearguard but took the lead after 65 minutes when home keeper Matt Turner allowed Gabriel Jesus' low shot to deflect in as it slipped through his legs at the near post.
Arsenal doubled their lead seven minutes later, cashing in ruthlessly on another Forest error after Gonzalo Montiel gifted possession to Martin Odegaard, his pass setting up Jesus to play in Bukayo Saka for a confident finish across Turner.
Forest substitute Taiwo Awoniyi grabbed one back with a close-range finish in the dying moments and almost levelled from a similar position just moments after, but Gunners keeper David Raya was equal to it.
Manager Mikel Arteta's celebrations at full-time illustrated just how much the win meant in a meeting with a Forest team whose victory here last season ended Arsenal's title challenge.
Liverpool could re-establish their five-point advantage over Arsenal with victory over Chelsea at Anfield on Wednesday, but this win provides the perfect platform for when Jurgen Klopp's side visit Emirates Stadium at the weekend.
Arsenal lacked urgency in the first 45 minutes, Forest digging in successfully and resisting any serious threat despite the visitors' dominating possession.
The stakes are getting higher and Arsenal simply had to provide more cutting edge after the break or risk leaving the City Ground without the three points they desperately required.
It was a far more dangerous Arsenal that re-emerged after the break, passing swiftly and more directly - a combination that proved too much for Forest.
The pressure was mounting, with Jesus rattling the bar from six yards and shooting over before he was the grateful beneficiary of the error from Turner, the former Arsenal keeper, who somehow allowed the ball to squirm into the net to end the stalemate.
Saka had threatened throughout, but even after he made it 2-0 Arsenal then had to survive five anxious minutes of stoppage time after Awoniyi forced his way on to Montiel's cross to give Forest hopes of an unlikely comeback.
The Gunners held out, Awoniyi scooping a chance into the arms of keeper Raya, and ended up celebrating at the City Ground - where they suffered so much pain at the end of last season.
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