The Russian Embassy tweeted an obviously computer generated image of three green and gray dump trucks hauling equipment with the message, "Extremists near Aleppo received several truckloads of chemical ammo." At the bottom of the image, in very small print, was a largely worthless disclaimer that read, "Used for illustration purposes only."
Kelsey D. Atherton, a writer for Popular Science, saw the tweet and quickly figured out that the image was a screenshot from the popular, long-running real-time strategy game Command and Conquer. Specifically, a screenshot used on the wiki entry for the game's Bomb Truck unit. After that, It didn't take the Twitterati long to jump into action.
For the rest of the day, various Twitter users responded to the Russian Embassy's tweet with screenshots of their own from games like Castle Wolfenstein, the various Battlefield and Call of Duty games, and even a group shot of a bunch of LEGO minifigs dressed up like "extremists".
The Russian Embassy has not yet tweeted about the responses to their use of the Command and Conquer image. They are likely scouring the Red Alert wiki for the proper image.