Napoleon came back from exile on Elba on March 1, 1815, landing in the south of France. He was declared an outlaw by the Congress of Vienna and the major European powers each pledged troops and money to depose him and restore the Bourbon dynasty to the French throne soon after Napoleon made landfall.
He ruled France til June 22 when he abdicated and was later sent packing to St. Helena in the South Atlantic.
Your challenge is this: Given a POD no earlier than Louis XVIII abdicating March 20, 1815 when Napoleon entered Paris, ensure that he stays on the throne of France despite the myriad challenges.