Concurrently, the refusal of Portugal to commit to the Continental System, and Spain's failure to maintain it led to the Peninsular War and the outbreak of the War of the Fifth Coalition. The French occupied Spain and formed a Spanish client kingdom, ending the alliance between the two. Heavy British involvement in the Iberian Peninsula soon followed while a British effort to capture Antwerp failed. Napoleon oversaw the situation in Iberia, defeating the Spanish, and expelling the British from the Peninsula. Austria, keen to recover territory lost during the War of the Third Coalition, invaded France's client states in Eastern Europe. Napoleon defeated the fifth coalition at Wagram.