Alloa failed to capitalise on their better league position, and it was Forfar who, in the opening minutes, had the Alloa defence under pressure.
Barry Sellars came close in the fifth minute when his fierce 15-yard shot was deflected by Dougie Hill for a corner and then three minutes later he again went near when his 16-yard shot was cleared from the line by Iain Nicholson.
Alloa settled into the match and in the 13th minute great play from Jamie Stevenson and Iain Nicholson saw both Andy Brown and Ross Hamilton miss from close range.
In the 30th minute Stevenson ran at the Forfar defence, beat three men and fired in a fierce shot from 16 yards which was brilliantly saved by Michael Brown in the Forfar goal.
Against the run of play Forfar snatched the lead in the 44th minute when Paul Shields brilliantly beat Hill and crossed to an unmarked David McClune, who steadied himself and fired past a helpless James Evans in the Alloa goal.
Forfar started the second half in total control of the match, but they were rocked when referee Allen, after consulting with his stand-side linesman following a goalmouth scramble, called over David Lowing and showed him a straight red card for violent conduct for a push on Alloa's Ross Hamilton.
Forfar refused to let the loss of Lowing affect them and increased their lead in the 56th minute when McClune scored his second of the day when he latched on to a long defensive clearance, ran 40 yards towards the Alloa goal and beat Evans with a fierce shot.
Alloa replaced Chris Townsley and Brown with Michael Daley and a trialist in an attempt to freshen up their side, but could not make an impression on Forfar.
In the end Forfar were worthy winners of this hard-fought match where there were more yellow and red cards than there were shots on target.