Soldiers who return from active duty with idea that they have 'seen it all, done it all'. The term is mostly used to describe those personnel who have seen what is often described as 'the Horrors of War' i.e. the death of fellow soldiers. These soldiers suffering from 'Squaddie Syndrome' will often exclaim that they are afraid of nothing...that seeing people die means they are able to make executive decisions over civialians simply because of what they have witnessed.
2. The term 'Squaddie Syndrome' has also extended beyond the military and into other areas of the public and private sector. It is used nowadays to describe anyone who insists they know everyhting therte is to know about their job, because of quasi-major incidents, when really the incident in question is anything other than major.
C1: "Having Swine Flu is Horrible!"
S= "Having Swine Flu is nothing compared to what we had to do"
C = Yeah but you knew what you were signing up for. Man, youo have serious Squaddie Syndrome