Currently you can purchase Modern Warfare II (2022) and III (2023) at no cost on the Xbox store, as the games are a play anywhere games, you can also play them both on the PC.
Given even the Xbox 360 Call of Duty games are still sold for £25 / $30 we are not sure if this is a mistake or not. Either way if you are interested I'd claim them sooner rather than later.
Update: Most of the game actually remains locked with only the "DMZ beta" content available to play, so keep that in mind before downloading.
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