In addition, most European countries which remain outside the EU are tied to it by economic agreements and treaties such as the European Economic Area. Although a number of former Soviet republics have joined the EU, or have taken steps to align themselves with various European organisations, Russia has maintained a level of independence from European institutions. Within the EEA, there have been no military conflict since 1945, making it the longest period of peace on the western European mainland since the Pax Romana.