Only You Can Prevent Friendly Casualties is one of the many trophy achievements within (COD) Call of Duty Vanguard, it requires you to throw smoke from the anti-tank ditch in order to provide cover for the charge
This specific trophy achievement can be unlocked during the Operation Tonga mission, where you will end up driving a truck and leading your troops to attack.
SOURCE: Gaming with Abyss
ONLY YOU CAN PREVENT FRIENDLY CASUALTIES
- During the second mission of the campaign, Operation Tonga, you will be required to drive a truck. However, before then make sure to take a few Smoke Grenades as we are definitely going to need those
- Then continue on and drive the truck until you find yourself in the ditch with your other fellow troops.
- Here lead the charge and make sure when your troops are running for the attack, now is the time to lob a few Smoke Grenades. The trophy achievement should then pop