On the Mission suez, at the end of the mission you have to make a choice between Hannah, or Irish, there is a third hidden option of not doing anything. Each of these choices will lead to a trophy
After EACH choice, you'll be awarded a dog tag during the credits.
Now if you want to try to get all three trophies, you can try to restart from checkpoint before the credits roll, it works "For tombstone" but I was not able to get it to work after "For the cause". However for this trophy that will NOT work, and might invalidate that run. (I didn't get a dog tag doing that, and didn't get the complete the game trophy until I beat the mission with out trying to restart checkpoint at the end).
You need to earn all three dog tags, and the dog tags are awarded after the checkpoint. As such you need to complete the Mission Suez once, and earn one of the dog tags (And one of the trophies). Then complete the mission a second time and choose a second option. Then complete the mission a third time and earn the third trophy.
This mission is short, and on easy it'll take you under 10 minutes if you know what you're doing. But there's mini cutscenes in the mission that take a while to go through.
On the third playthrough you'll earn the third dog tag, the third trophy, and this trophy will unlock right after that, during the credits.