Tom Clancy's The Division 2

“Operation Iron Horse is the second raid to be introduced in Tom Clancy's The Division 2. This raid takes Division agents out to a foundry that has been taken over by the True Sons to liberate it and put a wrench in the True Sons' plans by the request of a worker at the foundry by the name of Zach Young.” - The Division 2 Wiki

To unlock this achievement, you need to successfully complete the Operation Iron Horse raid with a team of eight players. It's also worth noting that you can join the game on the final boss via matchmaking (thus avoiding the need to fight the previous three bosses) and if the team is successful and there are eight of you when they are defeated, the achievement will still unlock. Where you are put in the raid, however, is completely random as is the nature of matchmaking.

First, communication is key if you want a successful run of this raid. It is important that everyone knows what everyone else is doing to coordinate attacks and objectives if you want to make it out alive. However, it is possible to be a mute while playing provided most people involved are somewhat versed in what needs to be done. Not very sportsman-like, though.

Second, to even begin the raid, you need to be in World Tier 5 or at least Level 30 in playing Discovery Mode and have a Gear Score of 490 or higher, with optimized high-end gear. If you haven’t attained one or both of these benchmarks, you will need to keep grinding out the main game’s missions to unlock higher levels and to find better equipment. It is also not much use to you or your potential teammates to just throw together what you have for the sake of getting a high enough Gear Score; you should try and make a competent character with weapons and equipment. High armor, armor regen and healing abilities are recommended as a priority, though damage to Elites is a huge advantage since most of the enemies will be armored to some degree. Once you have the required Gear Score and a competent character build, you're ready to take on the raid.

The raid is set in four encounters and each has a boss to defeat, each with increasing difficulty and dynamics. These aren't the same as the bosses from the main game that are simply high health and can be brought down by overwhelming firepower; they typically have a mechanic that needs to be exploited so that you can damage and defeat them. At this point, if you matchmake, you are likely to join a team of people who know what needs to be done, but it’s not guaranteed.

Note: If at any point your entire team is killed, you are reset to the beginning of the current stage. There are no checkpoints within stages.

For a detailed summary breakdown of all four encounters in this raid, head to the Strength In Numbers walkthrough guide. This is a tough raid, but with coordination, communication and teamwork, you can be successful. Good luck!