sentences:  He then studied law with Jacob R. Van Rensselaer, was admitted to the bar and commenced practice in Livingston, New York in 1806.Miller became active in politics as a member of the Democratic-Republican Party, and was a Justice of the Peace from 1804 to 1808.During the War of 1812 and the years immediately after, Miller served in the New York Militia, first as a Captain of Cavalry in 1st Squadron, 4th Regiment, 3rd Brigade and later as a Major in the 5th Cavalry Regiment.