Kevin-Prince Boateng’s spectacular opener, two goals from Robinho and a Zlatan Ibrahimovic penalty saw the Serie A champions put their Premier League visitors to the sword in the Champions League round of 16 tie at San Siro.
The result leaves Milan overwhelming favourites to progress from the second leg at the Emirates Stadium on March 6.
If they do so, it will be the first time in the last five seasons the Rossoneri have survived a Champions League meeting with English opposition, a sorry record for a club that dominated the competition for much of the previous decade.
Under coach Carlo Ancelotti, Milan lifted the Champions League trophy in 2003 and again in 2007.
They should have won in 2005, losing on penalties to Liverpool after that final in Istanbul.
Seemingly the continent’s preeminent force, their position at the top of the pile then came to an abrupt end.
As cross-city rivals Internazionale dominated the domestic landscape in the wake of the Calciopoli scandal, Milan surrendered their European crown with a 2-0 aggregate defeat to Arsenal in the 2007/08 round of 16.
That season they missed out on Champions League qualification following a fifth-place finish in Serie A, and were forced to accept UEFA Cup football in 2008/09.
Last year, it was the turn of Champions League debutantes Tottenham Hotspur to inflict a 1-0 aggregate defeat, with Milan bowing out yet again in the first knockout stage.
The most glaring cause of the Rossoneri’s toothless displays was the stagnation of their squad, as they continued to rely on much the same group of players who had captured the 2003 title.
Indeed, of the starting 11 and substitutes from their penalty shootout victory over Juventus at Old Trafford nine years ago, a remarkable six remain on the club’s books.
Wearied by age and slowed by injury, Gennaro Gattuso, Filippo Inzaghi, Clarence Seedorf, Alessandro Nesta and Massimo Ambrosini have played bit-part roles in the last two seasons, while fellow stalwart Andrea Pirlo was released only at the end of last term.
The sixth survivor, Christian Abbiati, was 25 in 2003, and has graduated to a role as first-choice goalkeeper.
Others, now retired, were retained beyond their prime, with the likes of Cafu, Paolo Maldini, Alessandro Costacurta and Serginho defying convention to hold down a regular berth well into their late 30s.
The obsession with age did not stop there. A revolving door of players, most of them deemed to have outlived their usefulness at other clubs, passed through San Siro in recent years.
Jaap Stam, Hernan Crespo, Rivaldo, Ronaldo, Ronaldinho and Emerson all arrived on the cheap, with mixed results.
The consequences of this approach were felt on the pitch, where Milan failed to compete with Inter domestically.
In Europe, the pace and high-tempo approach of English teams made it seem as though their opponents in red and black were standing still, totally ill-equipped to offer meaningful resistance.
It was a sorry state of affairs for a club once regarded as perennial Champions League contenders.
Last season, under the guidance of former Cagliari coach Allegri, the shoots of recovery blossomed into a first Scudetto since 2004.
The temptation to employ cut-price veterans remains, with Mark van Bommel and Antonio Cassano added to the squad in the last two years.
But the lessons of the past have been heeded.
The gradual introduction of Robinho, Alexandre Pato, Thiago Silva, Stephan El Shaarawy, Boateng, Antonio Nocerino and Urby Emmanuelson have lowered the average age of the squad, and provided a vital injection of pace and energy.
Milan received the rewards for their commitment to reinvention on Wednesday, as their sparkling new lineup demolished Arsenal in emphatic fashion.
After running holders Barcelona close in the group stages, this week’s performance was an unmistakable statement to the rest of the competition—Milan are back, and an eighth European crown could be within reach.