After being absent for a few years Call of Duty has returned to Steam with Call of Duty: Modern Warfare II — it's now available on Valve's storefront, but it is not compatible with the Steam Deck 'out of the box' — however, just because it's not Deck verified that's not to say those who own Valve's handheld are completely out of options.
Two names — Call of Duty: Modern Warfare II
First, just to clear up any potential confusion: yes, this is an all new game, but one with an old name. It is not a remaster of 2009's Call of Duty: Modern Warfare 2. Instead of just giving this action shooter its own unique title, Activision opted to just swap a decimal number for some roman numerals and call it a day. 🤷♂️
Can I play Call of Duty: Modern Warfare II on the Steam Deck?
Unless you want to do some tinkering, the short answer right now is no. Call of Duty: Modern Warfare II will not run on SteamOS. However, the long answer is yes — there is a way to get Modern Warfare II running on the Steam Deck...
Why can't you play Call of Duty: Modern Warfare II on the Steam Deck?
The key reason that, at launch at least, there's no official way to play this game on Valve's portable PC is fairly straightforward.
Call of Duty has kernel-level anti-cheat measures in place, known as Ricochet, that only work on the Windows version of the game.
The Steam Deck runs on a Linux-based operating system — and as such, due to the requirements for Ricochet, cannot run Call of Duty right now.
Marc-Alexandre Boulanger-Milot, a designer at Activision subsidary Beenox, has said that to play the game "you need to have the PC-developed kernel driver for anti-cheat", but suggested that Steam Deck play on the native SteamOS may "eventually" be supported.
How to play Call of Duty: Modern Warfare II on Steam Deck?
So, what's the workaround you need to get the game running? Well, you need to play it on Windows.
Thankfully you can install the Windows operating system on the Steam Deck, install the game on a microSD card, and run it that way.
This video shows the game in action on Windows 10, and offers some pointers on how to get it running on the Steam Deck:
Here's another video highlighing gameplay and performance on Windows 11 on Steam Deck. A few have noted that performance generally seems good, but load times are less than ideal.
It's worth noting that although plenty of folks have installed Windows on their Deck, you may face some issues - such as with driver support. Here's how to reinstall steamOS on your Steam Deck if need be.
The aforementioned Marc-Alexandre Boulanger-Milot from Beenox also detailed that those who do play the game this way "won’t face bans" for using such a workaround.
So, if you don't mind installing Windows on to your Steam Deck, you can join Captain John Price, John 'Soap' MacTavish, and others on a portable battlefield.