On December 16, 1811, the first of the New Madrid earthquakes shook the South and the Midwest. Many tribes took the earthquake as a vindication of Tenskwatawa's powers, seeing as a "call to action". They increased their attacks against American settlers and against isolated outposts in Indiana and the Illinois Territory, resulting in the deaths of many civilians. Tecumseh continued to play a major role in military operations on the frontier. By the time that the U.S. declared war on Great Britain in the War of 1812, Tecumseh's confederacy was ready to launch its own war against the United States – this time with the British in open alliance.