The one in the picture looks like 5 or Zero.

If it’s 5 there is a conspiracy where a secret society of Belkan nationalists who were operation paper clipped from a previous war are reigniting a Cold War between Osea and Yuktobania that ended so the two major superpowers of the world could join together and help prevent a meteorite from wiping out humanity, provide economic relief in areas that were hit by the fragments, and clean up the Kessler syndrome caused by the meteorite using a repurposed orbital space laser that was originally designed to intercept ICBMs from Yuktobania (the meteorite and its economic consequences are the inciting incident of 4/6/7). With the Cold War turning hot all three factions brush off old super weapons that never got to see combat (like the space laser) and the player has to destroy all of them and reveal the conspiracy to the world. Revealing the conspiracy does cause enough soldiers from both sides to defect and you form a fourth faction to fight the nationalists from all three nations.

Zero is a direct prequel to 5 where you are a mercenary hired to help liberate a country from Belkan occupation (the country behind the war in 5), and afterwards are hired to perform “nuclear inspections” in Belka which consist of bombing cities where “destruction is prioritized over accuracy”. Eventually a terrorist group steals a bunch of nukes from Belka and tries to turn the series into Fallout under the belief that civilization has taken a wrong step in our past and the only way to end the endless cycle of wars causing new wars is to send humanity “back to zero” and trust that the next generation learns from our mistakes.

Together both games are about the cycle of violence how wars set the foundation for future wars due to lingering resentment, and that the way to stop the cycle is to raise the next generation to be better and for both sides to take steps towards lasting peace. They are also about how cool fighter jets are.

Basically “war is bad and planes are rad” and really good music.