Since the end of the Cold War, and more importantly the removal of the former heavily guarded "Iron Curtain" separating Austria and its Eastern Bloc neighbours (Hungary and former Czechoslovakia), the Austrian military has been assisting Austrian border guards in trying to prevent border crossings by illegal immigrants. This assistance came to an end when Hungary and Slovakia joined the EU Schengen Area in 2008, for all intents and purposes abolishing "internal" border controls between treaty states. Some politicians have called for a prolongation of this mission, but the legality of this is heavily disputed. In accordance with the Austrian constitution, armed forces may only be deployed in a limited number of cases, mainly to defend the country and aid in cases of national emergency, such as in the wake of natural disasters. They may generally not be used as auxiliary police forces.