Reportedly deemed surplus to requirements at Old Trafford, the 23-year-old England international moved to the Emirates for £16 million, per Sami Mokbel in the Daily Mail.
The move came despite Wenger suggesting he would not be bringing in reinforcements after main striker Olivier Giroud picked up a long-term injury, per the Daily Telegraph's Henry Winter:
However, he should be well rewarded for bringing in Welbeck, who will likely take full advantage of Giroud's absence as he looks to establish himself in the Gunners side.
Welbeck is something of a divisive figure, with many rating him very highly while others believe he has not lived up to his early potential.
He is still a young man and should improve in the coming years—especially under Wenger's tutelage—and, more importantly, he will likely have the opportunity at Arsenal to play through the middle, his preferred position.
Welbeck was often used on the left flank at United, but it is as the main striker where he plays his best football, according to former Red Devils assistant manager Mike Phelan, per The Independent:
He is still only a young player and with young players you will get peaks and troughs but it is a case of Danny feeling more important in himself than he probably was over the last 12 months. He is in a position where he can play where he wants and I think that is why he chose Arsenal because they give him the opportunity to play in his best position, which is a striker.
Despite being played out of position for much of last season, he still managed to score nine goals in 25 Premier League appearances—10 of which were as a substitute, per WhoScored.com—with an impressive conversion rate, per Squawka:
If he is deployed as the main striker for Arsenal—as he should be—he should thrive with the service of Mesut Ozil, Alexis Sanchez and Theo Walcott and score bags of goals.
As sports journalist Sam Tighe points out, he is now playing at a club where he will be able to show his strengths, not necessarily always the situation at United:
Welbeck has pace, versatility, fine dribbling skills and something to prove, all attributes which should serve him well and make him a big asset at the Emirates.
After Giroud's injury, it looked as though Arsenal may be left with the unproven Yaya Sanogo as their only genuine strike option, a worrying situation for Gunners fans.
However, with the acquisition of Welbeck, they now have a player proven in the Premier League—and the Champions League—who will benefit hugely in the Arsenal setup.
He should prove a great success in North London, and Giroud may struggle to get his place back when he returns from his enforced break.