A 1970's era US military acronym, meaning: Strategic, Tough, and Ready Around the Clock. To be labeled "strac" was considered high praise.  "He was a strac trooper."

I'm not sure this is a valid definition, partly because it attributes it to a time period 10-15 years later than we used it.  It also - the internet tells me - is an acronym for a number of other military organizational usages, all falling somewhat in line with the definitions above.  I think they may have taken the earlier slang usage and formalized it to suit other purposes - look it up.

Stu