On 3 March 1813, after lengthy negotiations, the United Kingdom agreed to Swedish claims to Norway, Sweden entered a military alliance with the United Kingdom and declared war against France, liberating Swedish Pomerania shortly thereafter. On 17 March, King Frederick William III of Prussia published a call to arms to his subjects, An Mein Volk. Prussia had declared war on France on 13 March, which was received by the French on 16 March. The first armed conflict occurred on 5 April in the Battle of Möckern, where combined Prusso-Russian forces defeated French troops.