In the Wikipedia article on the RAF "Grand Slam" bomb that was used by the RAF in World War II, it is recorded that the bomb was used 42 times:
"By the end of the war, 42 Grand Slams had been dropped on active
service."
This caused me to wonder at the usage of "on" in this context. And then I was reminded of Ian Fleming's 10th James Bond novel, On Her Majesty's Secret Service. Here seems to be a similar usage of "on". In US English we would use "in" rather than "on", which leads me to believe that a British-English speaker has edited the Wikipedia article in question (or is that "on question"?). Because I would have written "had been dropped in active service." And I'm a Yank.
In the article about the bomb, the referenced sentence has the unfortunate suggestion that the bomb was actually dropped on something called "active service".
My question is (at long last), is this usage of "on" in the sentence above correct usage in British English, or did the writer get it wrong?
Best Answer
It wouldn't bother me whether OP's citation used on or in, but the evidence from NGrams suggests Brits in general very much favour the former...
...whereas Americans use both about equally often...
On reflection, I think I'm more likely to use on when referring to, for example, an actual soldier posted to a "tour of duty" overseas. And in when it's more figurative (such as a piece of antiquated office equipment that's still in daily use).