 Tilsit signified the high-water mark of the French Empire.In 1809, the Austrians and the British challenged the French again during the War of the Fifth Coalition, but Napoleon solidified his grip over Europe after triumphing at the Battle of Wagram in July.Napoleon then occupied the Iberian Peninsula, hoping to extend the Continental System and choke off British trade with the European mainland, and declared his brother Joseph Bonaparte the King of Spain in 1808.