On February 26, 1815, Napoleon managed to slip past his guards and somehow escape from Elba, slip past interception by a British ship, and return to France. Immediately, people and troops began to rally to the returned Emperor. French police forces were sent to arrest him, but upon arriving in his presence. they kneeled before him. Triumphantly, Napoleon returned to Paris on March 20, 1815. Paris welcomed him with celebration, and Louis XVIII, the new king, fled to Belgium. With Louis only just gone, Napoleon moved back into the Tuileries. The period known as the hundred days had begun.
Napoleon reclaimed Paris on March 20, 1815.
100 days from Napoleon's escape from Elba, the Battle of Waterloo occurred on June 18, 1815