In early 1814, the counter-invasion escalated when a successful Allied invasion of Napoleonic France opened a central front of the world war, forcing Napoleon's first abdication and ensuring the collapse of Napoleon'sEuropean empire following the Battle of Waterloo in the spring of 1815. In late 1943, the Allies began a two-year, multi-front counter-invasion of Europe to liberate the continent from Hitler's tyrannical empire. This turning point in the world war was marked by decisive Allied victories over Hitler's army in both the western and eastern European fronts. In late 1943, the Allies achieved stunning victories over Hitler's army in both the invasion of Italy on the western front and the Battle of Kursk on the eastern front, the latter of which was the largest conventional (non-urban) battle of the three-year conflict. Also in 1943, the counter-invasion was marked by a large escalation in the Allied aerial bombing campaign of Germany, producing the world's first manmade firestorm in Hamburg, Germany.
In response to the massive counter-invasion, in 1943 Hitler's chief ally Italy abandoned its war pact with him and sided with the invading Allies, opening a dreaded two-front invasion of Hitler's European empire that the war-depleted Nazi military could not repel.
In early 1944, the counter-invasion escalated when the successful Allied D-Day invasion of France opened a central front of the world war that ensured the collapse of Hitler's European empire by the spring of 1945.