I suppose this isn't technically story related but if you don't do what is necessary for this achievement stage 3 will be a pain in the ass. At the start Vantage will tell you to use the drones to scout around. Go to the first blinking dot it tells you to, using the scout drones. After some talking, you'll get a second dot, send the drones to it.
After some more talking the game will tell you to send some infiltrators down to the nearby node and take it. Once you have, you'll get this achievement. Taking the node disables the turrets at the bridge, which makes taking the nodes on the opposite side of it much, much easier.