The "Peace and safety" sign which Paul gave in 1 Thess.5 has never... happenned in the history of this world. There's always been wars and rumours of wars.
Most believe wars are going to continue all the way up to Christ's second coming. They are not; there's going to be a short period at the end just prior to Christ's return when all wars on earth will have stopped.
So, one of the most important things to consider about that short period of "Peace and safety", is just what... major event on earth would have to occur to really cause it?
Answer: the majority of the world truly believing that God has returned, and seeing some kind of proof of it.
That is what the devil is going to do for that short period of 'peace' at the end of this world, just prior to Christ's return. And it's going to fool the majority who are not paying attention to our Lord Jesus in His Word about it. Sadly, that is going to include many brethren that are deceived already, that expect the tribulation to be all out war and chaos up to Christ's return.