Why were the Napoleonic Wars fought? (1799 - 1815)?

Napoleon wanted to extend the territorial boundaries of France (he annexed a lot of territory directly to French control) and establish a political and military hegemony in Europe which he intended to be ruled as an empire by his and his family's direct descendants.

As the rest of Europe wasn't too keen on this, he imposed his policies by military aggression;the napoleonic Wars were the result of this aggression, and resistance to it and Napoleon's long term plans by other European states.

Before Napoleon took over the government of France, the revolutionary government already had the Army in Italy (this was where Napoleon gained his experience, in artillery). He continued the meddling in Italy. The Pope, in gratitude, consented to crown him Emperor.

Spain and Poland were kingdoms with unstable ruling families. France became involved with each when there was an open succession, putting in candidates to rival the Austrian ruling family. This, and an alliance with the Russians, helped start the major land wars. England entered as an ally to the Germans (Queen Victoria had relatives throughout the German states).

It was mostly about Napoleon's aggression in his conquests. The Napoleonic Wars were fought against Napoleon by the nations he attempted to conquer.

Napoleon had a hard time gathering enough troops willing to occupy a foreign nation. And when he did he selfishly invaded.