S1: At four O'clock this morning, Hitler attacked and invaded Russia. S6: Under its cloak of false confidence, the German armies drew up in immense strength along a line which stretches from the White Sea to the Black Sea. P: No complaint had been made by Germany of its non-fulfilment. Q: All his usual formalities of perfidy were observed with scrupulous technique. R: No one could have expected that Hitler would do it. S: A non-aggression treaty had been solemnly signed and was in force between the two countries. The correct sequence should be

S1: At four O'clock this morning, Hitler attacked and invaded Russia. S6: Under its cloak of false confidence, the German armies drew up in immense strength along a line which stretches from the White Sea to the Black Sea. P: No complaint had been made by Germany of its non-fulfilment. Q: All his usual formalities of perfidy were observed with scrupulous technique. R: No one could have expected that Hitler would do it. S: A non-aggression treaty had been solemnly signed and was in force between the two countries. The correct sequence should be