What does it mean by “ETSing”?

I’m reading a book and it’s a biography about a guy who was serving in Iraq. He wrote it while he was there. Anyway, I’m at a part where it says “He told us that everybody that was planning on ETSing (ETS: estimated time of separation) while in the theater is sh*t out of luck and that they are stop-lossing all of us”. I know what stop-lossing is, but what does it mean by “ETSing while in the theater”? Thanks for the help!

It means that the ETS date was while they were deployed to a combat zone…meaning they were due to separate from the military but couldn’t because they were in a combat zone

You are considered “in theater” when deployed to a combat zone such as Iraq or Afghanistan….you are in garrison when you are at your normal duty station

IAPMO ETS: The Water and Energy Connection: What Does it Mean for You? – Part One