World war had really been inevitable since the Soviet incursion into Yugoslavia on 27 July, the event which had brought about the first-ever direct clash between Soviet and United States troops on a battlefield. Moscow had long sought a favourable opportunity to reintegrate post-Tito Yugoslavia into the Warsaw Pact, in the confidence that the frailty of the union when its creator had gone would in good time furnish a suitable opening for intervention. As the cracks in Yugoslavia began to widen, particularly between Slovenia and the Federal Government in Belgrade, the Soviet sponsored so-called Committee for the Defence of Yugoslavia had most injudiciously staged an unsuccessful punitive raid into Slovenia. The Committee called for Soviet help and the opportunity was seen to be at hand. Within days Soviet units were in action against US forces from Italy. Fearful of the consequences if this crisis should get out of control, Washington had tried hard to cool it down and keep it quiet, but in vain, ENG (electronic newsgathering) film smuggled out by an enterprising Italian cameraman, showing US guided weapons destroying Soviet tanks in Slovenia, was flashed on TV screens across the world. Few viewers in the West even knew where Slovenia was. Fewer still doubted that the two superpowers were sliding with rising momentum towards world war.
There was no question where the focal point of any conflict between the armies of the two great power blocs would lie. It would be in the Federal Republic of Germany, where the Group of Soviet Forces in Germany (GSFG), largely stationed in what was known as the German Democratic Republic (GDR), faced the considerably weaker NATO forces of Allied Command Europe (ACE), in what NATO called its Central Region. It was in the GDR that the Warsaw Pact was even now staging manoeuvres of impressive size, so large as to arouse at first strong suspicion in the West, and then to confirm, that this was really mobilization in disguise. The manoeuvres had been notified to other powers, in accordance with the Final Act of the Helsinki Conference on Security and Co-operation in Europe. Some smaller though still considerable manoeuvres of the Southern Group of Soviet Forces in Hungary had not. It was from these that one airborne and two motor rifle divisions had moved into Yugoslavia.
The move into Yugoslavia was very nicely calculated by the Soviet Union. If the West did nothing to oppose it, a quick and easy gain would result, not of critical importance but useful, if only as a rough and timely warning to Warsaw Pact allies. If the West did oppose it with force, this would constitute an attack on a peace-loving socialist country that would justify the full-scale defensive action against NATO, as the aggressive instrument of Western imperialism, for which the Warsaw Pact was already in an advanced state of preparation. The fighting between Soviet and US forces in Yugoslavia could very easily be presented as evidence of imperialist aggression.
The war, which some believed had begun already in Polish shipyards, mines and factories the previous November,[2] was now a certainty and could not be long delayed. The NATO allies tried strenuously to complete their own mobilization, which had begun in the Federal Republic on 20 July, in the United States on 21 July, in Britain (where the co-operation of the trade unions — led by England’s leading Luddite-was not at first certain) on 23 July, with other allies following suit. In Britain in addition a strong and vigorous Territorial Army was constitutionally embodied and the lately formed but already highly effective volunteer Home Service Force, whose purpose was defence against both invasion by external forces and internal subversion, was activated.
The agreement of governments to evacuate from Germany the dependants of American and British service personnel and other civilian nationals was given, with inevitable reluctance, on 23 July, and they began to move out on 25 July. Reinforcements for the United States Army in Europe (USAREUR) began arriving by air from the United States on the same day, together with the first reservists for the formations in I and II British Corps, the latter, formed in Britain in 1983, having most fortunately been deployed in good (though not full) strength for exercises in Germany at the beginning of the month.