As a reward, Japan allowed Thailand to invade and annex the Shan States in northern Burma, and to resume sovereignty over the sultanates of northern Malaya which had previously been taken away in a treaty with Britain. In January 1942 Thailand actually declared war on Britain and the United States, but the Thai Ambassador in Washington, Seni Pramoj refused to deliver it to the State Department. Instead, Seni denounced the regime as illegal and formed a Seri Thai Movement in Washington. Pridi, by now serving in the role of an apparently powerless regent, led the resistance movement inside Thailand, while Queen Ramphaiphannee was the nominal head of the movement in Great Britain.