Time to use the horse.
Red Brass is one of the easier main missions you’ll get to undertake in Metal Gear Solid V: The Phantom Pain. For this operation, the only important piece of equipment you really need is your handy tranquilizer gun, unless, of course, you want to eliminate your targets with lethal means. Then, by all means, feel free to bring in a suppressed handgun or assault rifle, instead.
Your objective here is to eliminate three commanders. Whether you wish to kill them or send them back to Mother Base is entirely up to you. Once you’ve selected your landing zone, make your way to the objective marker. Your first target’s already at the location and the objective marker will point you towards the shack in which he’s hiding. As you approach the shack, tranquilize the guard standing right outside. Taking him out will attract the attention of the first commander and cause him to exit the shack. When he appears, quickly tranquilize him as well and Fulton him out before the other two targets show up.
After that, take your position near the large building with all the red Soviet flags. A jeep will soon pull up next outside the building, and you’ll see the second commander along with three bodyguards. The good news is that two of the bodyguards will wander off together, making it easier for you to take them out without attracting the attention of the other group. Once they’ve been taken care off, Fulton the second commander back to Mother Base and wait for your third commander.
Stay near the large building with the flags and another jeep will soon show up at your location. You can either repeat the same tactic you used with the second commander, or you can get Diamond Horse to take a crap in the middle of the road beforehand. Doing this will cause the third commander’s jeep to spin out of control, leaving him and his bodyguards disoriented. You’ll then be able to move in and extract him.
If you wish to fulfill the optional objective of listening to the commanders’ entire conversation before eliminating them, you’ll have to wait until all three all them arrive and enter the large building. To make things a little easier, you might want to consider taking out the rooftop guards first before going in for the commanders. Once the commanders are done with their meeting, there are two viable methods you can employ to eliminate them. You can either run in and tranquilize them quickly with Reflex Mode, or you can lure them out one by one by knocking on the wall outside.
Once you’ve eliminated all three commanders, get out of the hot zone and you’ll have accomplished your mission. Completing Red Brass will unlock the Medical Unit for Mother Base, and Kaz will also pull in resources to construct a new platform for the new unit.