Which battle in 1809 forced Austria to sue for peace?

The Battle of Wagram forced Austria to sue for peace in 1809.

Fought on 5–6 July 1809 near Vienna, Wagram was a costly French victory over the Austrian army commanded by Archduke Charles. Napoleon assembled a huge multinational force after recovering from Austria’s surprise victory at Aspern-Essling in May.

Wagram did not produce an immediate peace treaty. Austria still possessed a coherent army, so Archduke Charles withdrew toward Bohemia. However, the defeat badly damaged Austrian morale and made continued resistance increasingly difficult. Charles requested an armistice at Znaim while the fighting was still effectively being concluded.

The eventual Treaty of Schönbrunn, signed in October 1809, ended the War of the Fifth Coalition. Austria surrendered territory, lost influence, and accepted heavy financial and political penalties. Aspern-Essling is a common mix-up: it was Napoleon’s major defeat before Wagram, not the battle that compelled Austria to seek peace.