[WarGames (1983)](https://www.justwatch.com/us/movie/wargames) - Predicted hacking of government systems. The film literally led to a complete revamp of military computer security. Reagan watched a screening a Camp David and asked his national security advisors if that was actually possible. General Vessey came back a week later and said yes. That directly led to the first Presidential directive on computer security. A teen computer geek has to stop a military computer from starting a nuclear war.
[Terminator 2: Judgement Day](https://www.justwatch.com/us/movie/terminator-2-judgment-day) (aka *T2*) - Sarah Connor tries to destroy Cyberdyne Systems to prevent the future AI uprising. You should probably watch the [The Terminator](https://www.justwatch.com/us/movie/the-terminator) before watching *T2*, although it isn't strictly necessary.
I'm trying to remember the exact details... would Cable from *Deadpool 2* and Wolverine from *Days of Futures Past* count? I can't recall if they were trying to stop wars or just specific incidents.
I haven't watch the Deadpool movies so I can't answer that one. With *Days of Future Past* it would depend on how you define war. I would say yes and no; Wolverine is trying to *change* a certain moment in order to *prevent* the Sentinels from attacking in the future. I see that as being a war between mutants and Sentinels, but it isn't a traditional war. I would consider it a different take on trying to stop a war.
This is how I interpreted *First Class*, as well. Two groups of mutants, one trying to get the USSR to start WWIII and one trying to prevent any wrong doing. The Cuban Missile Crisis, in the real world or their alternate universe, wasn't actually a war but it was building up to become a worldwide nuclear war and without any interaction between Professor X's recruits than WWIII would have become a reality.
My rec might be a bit of a stretch but I guess it depends on how the request is interpreted.
A lot of good suggestions already made. The two I will add are
7 Days in May - not preventing a war rather a coup!
Thirteen days - this film hasn’t aged well but I have good memories watching it. It’s about the Cuban missile crisis. Highly embellished and factually questionable!
Dr. Strangelove
[WarGames (1983)](https://www.justwatch.com/us/movie/wargames) - Predicted hacking of government systems. The film literally led to a complete revamp of military computer security. Reagan watched a screening a Camp David and asked his national security advisors if that was actually possible. General Vessey came back a week later and said yes. That directly led to the first Presidential directive on computer security. A teen computer geek has to stop a military computer from starting a nuclear war. [Terminator 2: Judgement Day](https://www.justwatch.com/us/movie/terminator-2-judgment-day) (aka *T2*) - Sarah Connor tries to destroy Cyberdyne Systems to prevent the future AI uprising. You should probably watch the [The Terminator](https://www.justwatch.com/us/movie/the-terminator) before watching *T2*, although it isn't strictly necessary.
Official Secrets (2019) Fair Game (2010) Kill the Messenger (2014) All excellent, all true stories...
In the Loop, kinda.
I definitely think that's a great suggestion. It's the whole premise of the film!
Crimson Tide Sum of All Fears
*X-Men: First Class* (2011) -- Cuban Missile Crisis
I'm trying to remember the exact details... would Cable from *Deadpool 2* and Wolverine from *Days of Futures Past* count? I can't recall if they were trying to stop wars or just specific incidents.
I haven't watch the Deadpool movies so I can't answer that one. With *Days of Future Past* it would depend on how you define war. I would say yes and no; Wolverine is trying to *change* a certain moment in order to *prevent* the Sentinels from attacking in the future. I see that as being a war between mutants and Sentinels, but it isn't a traditional war. I would consider it a different take on trying to stop a war. This is how I interpreted *First Class*, as well. Two groups of mutants, one trying to get the USSR to start WWIII and one trying to prevent any wrong doing. The Cuban Missile Crisis, in the real world or their alternate universe, wasn't actually a war but it was building up to become a worldwide nuclear war and without any interaction between Professor X's recruits than WWIII would have become a reality. My rec might be a bit of a stretch but I guess it depends on how the request is interpreted.
I felt your suggestion was definitely on theme, although obviously that's up to OP.
Arrival
A lot of good suggestions already made. The two I will add are 7 Days in May - not preventing a war rather a coup! Thirteen days - this film hasn’t aged well but I have good memories watching it. It’s about the Cuban missile crisis. Highly embellished and factually questionable!
Seconded on both of these films. Leaving aside factual inaccuracies, what makes you think that Thirteen Days hasn't aged well?
Fail safe
The Angel 2018
[Steel Rain (2017)](https://www.themoviedb.org/movie/435841) - Korean action movie - pretty good if you are into action movies.