Lynch joined the Army from Chicago in 1964, and by December 15, 1967, was serving as a specialist four in Company D, 1st Battalion (Airmobile), 12th Cavalry Regiment, 1st Cavalry Division (Airmobile).
Soldiers from the 1st Brigade, 1st Cavalry Division including 1st battalion 12th Cavalry Regiment and 2nd Battalion, 5th Cavalry Regiment were stationed at Camp War Eagle and fought against the shia Militia of Muqtada al Sadr known as the Mahdi Army during the uprising which began April 4, 2004.
By February 10, 1970, he was stationed in Vietnam as a Specialist Four with Company D of the 1st Battalion, 12th Cavalry Regiment, 1st Cavalry Division.
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A last-ditch attempt was made by Kartar Singh and Pingle to trigger a mutiny in the 12th Cavalry regiment at Meerut.