An army of the French Empire led by Marshal André Masséna marched from northern Italy into the Kingdom of Naples, an ally of the Coalition against France ruled by King Ferdinand IV. The Neapolitan army was vanquished at Campo Tenese and rapidly disintegrated. The invasion was eventually successful despite some setbacks, including the prolonged Siege of Gaeta, the British victory at Maida, and a stubborn guerrilla war by the peasantry against the French. Total success eluded the French because Ferdinand withdrew to his domain in Sicily where he was protected by the Royal Navy and a British Army garrison. In 1806 Emperor Napoleon appointed his brother Joseph Bonaparte to rule over southern Italy as king.