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The invasion of Spain was caused by the Peninsular War, a long military conflict between France and the allied forces of Spain, United Kingdom and Portugal. Allies at the point, France turned on Spain at the beginning of the war. The war on the Peninsular lasted until the sixth coalition, and those years of fighting put a heavy strain on France's armies. Battles were won by the French, on the other hand, their resources were the cause for concern. The Spanish armies were continuously beaten, however, they persisted to hound the French. The drained and unnerved French armies were eventually driven out of Madrid and back to France by the combined allied armies of Great Britain, Portugal and Spain. .
Napoleon's invasion of Russia in 1812 proved to be the major turning point in the Napoleonic Wars. Following Russia's renewed trade with the British, Napoleon pressed for invasion of Russia. Napoleon navigated the Grande Armee through long journeys in attempts to bring Russia to battle. As Russia retreated deeper, Napoleon I pressed his army further. All while the Russians used unprecedented measures of burning villages, towns, and crops to prevent Napoleon's army from living off the land. .
These tactics and Battles with the Russians proved to be costly for the large French army; resulting in over seventy-five percent casualties from the Grande Armee which once numbered nearly half a million soldiers. Not even six months passed from the beginning of that invasion that, Napoleon's army, beaten and drastically diminished left Russian soil. This campaign, prompted the dramatic shift of power in Europe. Prussia and Austria, broke their alliances with France, and switched teams, causing the outbreak of the War of the Sixth Coalition. Ultimately leading to Napoleon's defeat at Leipzig and later Waterloo. .
Following a devastating defeat at the hands of the British Naval forces, Napoleon's idea for economic warfare against the British though seemed impervious it would turn out to be very costly.