It was, of course, only a very small operation from their point of view, but to Earth it was the biggest thing that had ever happened.
There had been no warning when the great ships came pouring out of the unknown depths of space. Countless times this day had been described in fiction, but no-one had really believed that it would ever come.
Now it had dawned at last: the gleaming, silent shapes hanging over every land were the symbol of a science that Man could not hope to match for centuries to come. -- Author C. Clark, EARTH AND THE OVERLORDS, Chapter 2