If Iran refuses to turn over the 15 British sailors and marines, is this a declaration of war?

We must learn from the lessons of history. When that fool Neville Chamberlain believed he could appease Hitler and it would stop him, look how that turned out. The Iranians have refused to stop enriching Uranium despite overwhelming international demand, and now they illegally seize 15 Britons. Is it time we stop showing weakness and do the right thing and stand up and fight? or should we remain cowards and continue appeasing the enemies of the civilized world?