Exodus (Side Mission)
After recruiting Grace in the Grace Under Fire Mission, return to the Lamb of God Church where a new side mission has appeared.
Talk to the soldier there to launch this (side) rescue mission.
Follow your marker down to the Sacristy, and give the area a good scan before wading in- hostiles will kill hostages if they're spooked. In particular, watch out for the VIP, who will be one of the two hostiles at the water's edge.
Rather than using the zipline, it's easiest to start with the three hostiles at the north end (including the VIP). If you coordinate with your companions, you can take out all five almost simultaneously. The chain takedown perk is also useful here.
Free the hostages. You might also want to check in the small chapel here- there's a boar hunting magazine in the corner by the guitar.
Escort the ex-captive toward the marker. They'll follow you like ducklings.
Six hostiles will attack on this side of the river, but no specialists. With the thick grass here, you can snipe them almost before you can see them. Sniping is good, because it keeps you from accidentally losing a hostage in combat.
Past the ambush is a boat you can use to cross the river. The boat seats four plus a pilot, so if you rescued all the hostages and have two companions, then somebody has to swim.
There's another group of hostiles on the far shore, but they're as disorganized and snipable as the first bunch.
Take your soldiers the final few meters to the weapons cache for mission completion.
You can loot some of the copious ammo here before you go. Watch for bears.