On 18 June, the French suffered a defeat at the Battle of Trebbia, and consequently the Austrians were able to move more decisively against Mantua. On 4 July the siege entered a new stage, with Austrian reinforcements arriving, and the besieging force growing from 8,000 to 40,000. The Austrians were commanded by Hungarian general Baron Pal von Kray, an artillery expert. Artillery bombardment was constant. On 24-25 July the assault begun; and the Austrians slowly advanced over the next few days. On 27 July Foissac-Latour began negotiating surrender terms.