In 1810, the French Empire reached its greatest extent. On the continent, the British and Portuguese remained restricted to the area around Lisbon and to besieged Cadiz. Napoleon married Marie-Louise, an Austrian Archduchess, with the aim of ensuring a more stable alliance with Austria and of providing the Emperor with an heir. As well as the French Empire, Napoleon controlled the Swiss Confederation, the Confederation of the Rhine, the Duchy of Warsaw and the Kingdom of Italy. Territories allied with the French included: the Kingdom of Spain, the Kingdom of Westphalia, the Kingdom of Naples, the Principality of Lucca and Piombino, and Napoleon's former enemies, Prussia and Austria. Denmark–Norway also allied with France in opposition to Great Britain and Sweden in the Gunboat War.