I’ve never heard that term before. Exactly what does it mean? Is it vulgar?
It means to wholeheartedly throw oneself into a situation which sucks, but is necessary (or at least, unavoidable). “The suck” is the hardship (physical, mental, emotional) experienced by people who are trying to do something difficult, and worthwhile, and dangerous. Soldiers are a prime example of such people.
One Interpretation
Unofficial slang term used by the Marine Corps. Defines any situation in and around a war time conflict where conditions are undesirable. Also known as "The Shit." "Welcome to the Suck..." or "You are in the Shit..