United's half-time lead was fully deserved, but it was Arsenal who began the second period with the greater purpose. Mesut Ozil thrashed a close-range effort into David De Gea's side netting to serve notice of the Gunners' growing intent, although Rooney's low, left-footed effort came within a whisker of doubling the Reds' advantage on the hour.
For the most part, Arsenal were on the front foot and United, backed by a wall of noise from the home support, were required to put in a dogged defensive shift, with Jones - returned to centre-back after an injury to Nemanja Vidic - particularly outstanding.
Chris Smalling headed wastefully wide from a quick van Persie free-kick nine minutes from time, but quickly atoned with a brilliant block to save the day as Giroud looked set to haul the visitors level. That intervention typified United's play on an afternoon when the champions laid bare their mettle for all to see.