To ride shanks mare is slang for walking. Shanks = legs.
Between 1958 and 1966 I spent the majority of my time out of the country. On three occasions I found myself wishing I were somewhere else. Once in Africa, then Berlin, then South America. Most jobs were easy money, but sometimes they weren't.
Oh - thanks for explaining. LOL. I really thought it was a donkey.
I can well imagine that there were times you were in a difficult spot in those countries and without the technology and communication available to our military today, it must have been, well, I'd say frightening, but you're a guy and probably wouldn't admit to that. So I'll just say it was probably challenging.