I agree with the original poster to the extent that a number should not come directly before the plural form, "troops." If you can't say 1 troop, meaning one person in the armed forces, then you can't say 4 troops, meaning 4 people in the armed forces. This was a recent editorial decision with only some of the news agencies, and one that I do not agree with.

We should not say, "4 troops were killed" in any case. It may be true that a Marine or a soldier would want "troops" replaced by "Marines" or "soldiers," and saying 1 Marine and 1 soldier is grammatically possible in English.

A possible compromise might be "4 of our troops were killed," which sort of skirts the grammar issue by picking individuals out of a group using the word "of," as in the examples given in the previous post by Warsaw Will. 4 of our flock, 4 of our team, 4 0f our pride (or lions) are all possible even though the group word cannot mean one individual.