Arsenal had waited a long time for this. It was 14 years since they claimed three points at Old Trafford, 30 league games since they won away at any of the big six. Mikel Arteta had secured flagship wins against the elite clubs at the Emirates Stadium and Wembley.
Now he has one on enemy territory, too, and a manager whose first win came against Manchester United, back in January, had another landmark triumph. After 1-0 defeats in their previous two league games, Arsenal could savour the scoreline.
But for United, the lack of home comforts is an ever greater concern. They may have walloped RB Leipzig 5-0 but they are yet to beat English opposition at Old Trafford this season.
Arsenal became the third visitors from the capital to win and while this was the first time since 1936 they had kicked off against the Gunners with both sides in the lower half of the table, only United were marooned there at the final whistle. It was a wretched 100th game in charge for Ole Gunnar Solskjaer. His side were mediocre.
For Arteta, it was a tactical triumph. Arsenal were so impressive in the first half that they forced United to change shape. They got their reward in the second.
If creating chances for their most potent finisher has been one of their problems, Pierre-Emerick Aubameyang ended his longest Premier League goal drought.
The Arsenal captain had not struck since the opening-day win at Fulham but he sent David de Gea the wrong way from 12 yards. He was aided by United’s record signing, whose comeback to the league starting 11 was an unhappy affair.
Paul Pogba was dropped after the 6-1 defeat to Tottenham. Recalled, he conceded a penalty by catching Hector Bellerin. Nor did Pogba have much else to enjoy. Solskjaer retained the diamond system in midfield that had worked so well against Leipzig. This particular diamond was not forever; indeed, it only lasted 45 minutes.
In theory, United had a numerical advantage in the centre of midfield but Arsenal imposed themselves. They pressed high up the pitch and disrupted United’s rhythm. They possessed the game’s outstanding player.
Thomas Partey’s energy and ability to regain the ball explained why Arteta wanted him, but he also instigated attacks with progressive passing and stung the palms of David de Gea with a fiercely-struck shot. Arteta, who had sprung a surprise by omitting both of Granit Xhaka and Dani Ceballos to pair Partey with Mohamed Elneny, was justified.
Behind them, a fit-again Rob Holding and Gabriel were booked in quick succession with an hour remaining. The Brazilian was spared a second yellow card for a foul on Mason Greenwood later; otherwise, though, each excelled.
Greenwood and Marcus Rashford were so starved of service before the break that when they combined it produced United’s sole shot of any variety before the break. Rashford curled a low pass through the Arsenal defence. Greenwood met it with a first-time shot that Bernd Leno blocked at his near post.
When United returned for the second half, it was playing 4-2-3-1. They posed more of a threat and Harry Maguire looped a header wide from Luke Shaw’s free kick but the closest they came, in the final minutes, was when Elneny and Leno deflected Donny van de Beek’s cross on to the post.
And Arsenal had merited their lead. They had almost gone ahead earlier. Goals have been in short supply but Willian was agonisingly close to a first for his new club.
The Brazilian had begun by coughing up possession time and again. He impressed rather more by linking up with Aubameyang, who backheeled a return pass. The former Chelsea winger’s rising shot clipped the bar on its way over.
Willian was involved again when Hector Bellerin crossed and United’s static defence afforded Bukayo Saka a free header. He, too, cleared the bar.
Aubameyang’s radar was awry when he curled a shot wide after being found by Alexandre Lacazette. But when he struck, Arsenal had their first league win at Old Trafford since another African attacker, Emmanuel Adebayor, scored in 2006.