Mission 10: Downtown District
When you get control run up to the top of the theatre and look into the lobby. LOTs of enemies. This is a good time to spam frag, remote, and prox grenades. You'll get reloaded before you need them again. Spamming grenades it's hard to leave one to Takedown but you don't need to worry about it at this time. Once everyone is dead head out into the streets and go into a little walking cutscene.
As you gain control again head down the alley but crouch before turning the corner. Wait for the guard to engage the civilian and then head up the pipe. Left all the way around the building and then drop one level so that you can go to the next building. Pull yourself up to the top ledge area and work your way to the outside of the building. I do a Death From Above followed by a couple of quick shots and then high tail it out of there. This is another area where you can bypass a lot of enemies by just shooting and running.
Reload at the weapons stash and then head down the right side and climb the scaffolding. We can't kill any innocents so the best course of action is to headshot the guy speaking. Then frag the rest. Afterward head back and reload at the weapon stash and then it's off towards the White House.
Downtown - The Theatre
Hug the right side of the street and crouch roll all the way to the speed limit sign and Takedown the guy there. Then back to the sidewalk and continue your long trek around the outside to keep from getting seen. Blow up the tanker from back here by the Humvee and then sneak in the backdoor area by the map.
Head around the back side of the small building by the ATV. This is another area that, when the coast is clear, simply run through the gate and by pass everyone.
Then head left down the stone path to bypass even more guys. Pause at the middle because 50% of the time a single enemy may come down the left path. Then crouch roll past the humvees to the next area hugging the right side. Go behind the little guard house to the hedgerow and M&E the four closest to you. Then just shoot down the last couple and move on.
Hug the back hedges in front of the White House and move to the right. Wait for the guards to pass and just head around everyone and get inside.
Downtown - Getting To The White House