You would be correct. It's a fun series, Otto has all kinds of interesting adventures. He gets his start as a submarine captain in the Austro-Hungarian navy in WW1, later gets transferred to the Flying Corps and becomes a pilot, and goes on to have other adventures in various and sundry places over the next couple of decades.

The stories are cast as his memoirs, written (or dictated) at the age of a hundred and one, as he is nearing death in a British nursing home sometime in the late 1980's.

(One young nurse is rather taken aback by his claim to have been a submariner for Austria, since it's landlocked... well, it is -today-, but in 1914...)