US officials said Tuesday that two American citizens who joined the Syrian Kurdish YPG militia earlier this year were killed last week during the fighting to liberate the city of Raqqa from ISIS. They were identified as 29-year old US Army veteran Nicholas Warden and 28-year-old Robert Grodt. A statement by the YPG said that British citizen Luke Rutter was killed along with Warden and Grodt. About a dozen Americans are said to have lost their lives while fighting alongside the YPG.