Greece Declares War On Europe?

Sort of.

Although, this is more like a "Samson Strategy", pulling all the walls down, than it is a real war tactic.

BusinessInsider: Greece's defence minister is threatening to 'flood Europe with migrants'

Kammenos, who is a member of the Greek government's junior coalition party Independent Greeks, said that "If Europe leaves us in the crisis, we will flood it with migrants, and even worse for Berlin if in that wave of millions of economic migrants there will be some jihadis of the Islamic State too," according to the Italian newspaper La Repubblica. 

He went on explaining that: "If they [the Eurogroup] strike us, we will strike them. We will give to migrants from everywhere the documents they need to travel in the Schengen area, so that the human wave could go straight to Berlin."