United made a fantastic start by forcing a corner in the first five minutes of the game when Chris Smalling had a chance to swirl the ball over the line but his effort was nipped on the line.
It was all going fine until the 20th minute when the infamous animosity between the two sides surfaced after Edin Dzeko and Anderson clashed over a tackle. Each of them earned a yellow card for their angry reactions.
United still continued to dominate the game until City broke the deadlock when Joleon Lescott gave a skilful miss to his marker to meet Silva"s in-swinging free-kick to place a precision header into the top corner.
City soon went 2-0 up when they netted another one just on the stroke of half-time. A powerful swerving shot from Dzeko zoomed past David de Gea into the goal post.
Sir Alex Ferguson, then replaced his side with some youth power after getting in Phil Jones, Jonny Evans and Tom Cleverley - all replacing more experienced heads at the break.
However, all that changed dramatically after a late show of aggression by United, who drew their first blood when Smalling pulled off a stylish mid-air finish. Minutes later, City were jolted again when Cleverley, Welbeck and Rooney combined with a scathing series of quick passes on the edge of the box that prepared Nani for a decisive finish.
Some thrilling moments later, Nani struck the decisive goal to give United a fantastic victory over their arch-rivals.
A visibly excited Sir Alex Ferguson, later said, "It was a very good performance in terms of our football, I couldn't believe we were 2-0 down at halftime. But the players kept their heads, kept playing football and got the result they deserved. They have courage to keep the ball and are not admitted by tough tackling."