Wurmser was reinforced once again to compensate for some 20,000 losses sustained in the past two months and made an attempt to relieve the siege of Mantua. Some 45,000 Austrian troops were left behind to guard against any new French offensive whilst the main body of the Austrian army moved on Mantua. At Rovereto on 4 September, Bonaparte inflicted a heavy defeat on the Austrians and was then well-placed to strike at the rear of Wurmser's army. Reacting slowly to this new threat, the Austrians were again defeated at the Battle of Bassano, where their army was reduced to just 12,000. The remaining troops marched rapidly towards Mantua, but became trapped there by General Masséna's advance party.