Coming after the end of one significant historical epoch (the post-World War II consensus) and in the middle of what followed (a free enterprise boom), the fall of the Berlin Wall was a surprise that caught most observers off-guard.
To those in Western intelligence circles, the opening of the East German border, and just how it opened - chaotically, without fanfare and apparently at random - was a warning that the assumptions which had underpinned policy towards the communist East and the Soviet Union, in particular, were fatally flawed.
That shock would soon be replaced by self-congratulation at the 'End to history' (or even, in it's most naive form, a 'Holiday from history') as it seemed, for a while, that democratic values had conquered the world.
Heady and optimistic times, indeed.