That looks like a feature of the Religious Leagues. If Austria is attacked as Emperor and Leader of the Catholic League then all League Members are called in as allies.
Bohemia is the Protestant leader though and not involved. It must have been a coalition. I don't see the coalition icon but that probably goes away when the war starts. However, if France is in the Protestant league and attacks the Catholic leader does that bring the whole league in? This has got to be the most one-sided war against France I've ever seen.
Attacker: France (GP)
Defender: Castille/Aragon (GP), Commonwealth (GP), Austria/Hungary (GP), Denmark/Sweden (GP), England (GP if not for PU)