American Fugitive

The easiest way to do this is if you use your phone to order a tank.
I don’t think it matters which island you are on but pick an area that has some open fields.
Get your wanted level up by firing off some rounds and wait for a tank to show up. It might take a minute before one shows up, just keep moving around. They will send in cops and then the SWAT vans and jeeps. Once a tank shows up just stay out of its range (a red circle will show where it will fire next). If you keep moving you can probably destroy about 7/8 tanks before you need to get a new one. I let my tank get down to 2 green bars of health before getting a new one, since after that it slows down quite a lot and is harder to avoid the tanks fire.

Now here’s the good part. You don’t need to order a new one. Just wait for the next tank to show up and car-jack it.

The main thing to do is ‘JUST KEEP MOVING’.

Jump into the new tank and Be careful of the cops on foot. They are the only thing that will try and pull you out of the tank you are in. Just run them down. :)

This is a bit of a grind but not too bad, i personally found the other solutions too slow. The best way i found way to do the fog of war challenge on the first map just below and right of the car dealership. You get 2-4 tanks every 2 mins using the bazooka. Make sure you have your health upgraded and when you get down to last 15 seconds pause and restart challenge. This was my last ach and took 30 mins or so

I found it easier to grab the tank in the base at the top left of the first map. You instantly get a six-star wanted level needed to spawn enemy tanks. You want to not drive too far and instead stay in a small area. If you get too far from the chopper and cops they're prone to lose sight of you and delay tanks from spawning.

When your tank's health is low, either wait until another tank shows up and carjack it or go back and get another from the base. Note that you don't get credit for shooting an empty tank so shooting the tank at the base doesn't count.

You can check progress by pressing and using / to go to the Statistics tab.

You can also combine this with the Rollin' Rollin' Rollin' achievement where you need to crush 250 cars:



Take the tank across the bridge and to the used car lot. Much easier to crush parked cars than moving cars. Here's a video: