Excerpts from Books and Wikipedia
"Russian Emperor Alexander I, King Frederick William III of Prussia and Austria and commander Prince Schwarzenberg, and their respective armies, marched unopposed into the French capital on March 31, 1814. The keys were surrendered by Prince Talleyrand, once Napoleon's foreign minister.… Despite a brilliant campaign against the invaders, Napoleon wasn't able to prevent the Russians, Prussians, and Austrians from marching directly on his capital while he was organizing further operations from the château at Fontainebleau, south of Paris. Realizing his commanders were no longer all with him, Napoleon bade farewell to his guard and abdicated his throne on April 6." [1001 Days]