Peregrina I have yet to hear them tell me how exactly NATO kept the peace between France and Germany/German speaking states in the past, when they have been fighting each other for centuries.
NATO was founded in 1949, before the ECSC in 1951. NATO keeps the peace in Europe by NATO nations signing up to Article 5 , so an attack on one is an attack on all. This dealt with the issue of Germany from 49-55 as West Germany didn't join til 55, and East Germany was behind the Iron Curtain under the Warsaw Pact. Had E Germany attacked France, W Germany etc, then the Allies would have ridden to the rescue, and would the Warsaw Pact/the USSR states have really wanted to take on the US? NATO and the Warsaw Pact co-existed as we had the idea of MAD, so the Cold War never really heated up to full boiling point, just got to a rising simmer at times.
When the reunification of Germany happened, the whole of Germany became a NATO nation.
France chose to remove itself from some of the NATO structures in 1966, and fully rejoined in 2009. As it still participated in some NATO structures, in which it was allied with Germany, from 1955 onwards, there was no option but to cooperate, unless you wanted to be outside the idea of collective defence and the nuclear umbrella of the US, which was the best defence against the USSR.
If you care to do some digging around the RUSI website; the NATO website etc, you will see quite clearly how it has worked.