A good place to get this is on the first level. After making your way through the embassy and heading downstairs you will come to a circular courtyard flanked by two guard towers.
Lots of trucks will start piling in full of enemy troops. Take cover on the left by the sandbags until all the troops are off the trucks and in the middle area. Cook a frag and hope for the best, may take a few tries but you will get there.
Might be a good idea to pick off the guys in the towers while in cover so as you do not get shot trying to throw your 'nade.