Scrap your knowledge of the last bits of the Cold War. Let's say that the USSR and the Eastern Block didn't go tits up in the late 80s. How is not important. All that is important is the reality of this scenario. The USSR still holds a dominant position in the world, periodically sparring with NATO through proxies, such as in Syria and nearly in Libya. But the tensest area of the cold war, the iron curtain, still stands in all its glory - or shame, depending on which side you stand.
From time to time, NATO holds readiness exercises simulated to be as real as possible. But without informing the USSR of anything, a set of exercises commenced. A large buildup of troops from European NATO countries in West Germany, France, and the Benelux, and Exercise REFORGER taking place in rapid succession was to be expected. But on the Turkish-Soviet border, troops assembled too, and in the pacific the US navy and the Japanese Naval Self-Defence Force assembled the world's most powerful armada and acted agressively as to test the Soviet Coastal Defence's initial response to a perceived naval attack. All the while Presidents and Prime Ministers went into hiding.
The Warsaw Pact, not being informed of anything, made a hot-headed but not wholly unreasonable conclusion: It was the first stage of a madman's war against the USSR. And so, the Pact responded. The armies were mobilised and reservists called, and on November 10th the command was given for pre-emptive attacks against the amassing NATO forces. At 2AM, the first NATO units came under attack by East German and Soviet forces in the Fulda Gap - More contacts rapidly followed later. Shit had seriously hit the fan.
So basically, this plays out in the inner-German border either around Hamburg or around Fulda. While I won't allow the alien space bats to come over, nor any Mary Sues/Gary Stus, I'm going to be relaxed on character-building but will of course lend a hand if needed. All the shit we use today is being used, and because it's 2015 we can freely use Wikimapia to determine the location of things.