On Feb 4 one of the four satellites operated by Maxar, a company based in Colorado which photographs more than three million square kilometres of the earth every day, took pictures of a Russian military camp in Rechitsa, Belarus. Rows of military vehicles were laid out neatly over a thick carpet of snow less than 50km from the border with Ukraine. On Feb 14, a sister satellite took another picture of Rechitsa. The snow had gone; so, too, had most of the vehicles.
Since the start of the Cold War, America and its Nato allies have scrutinised Russian military deployments and movements using expensive and often exotic means of keeping tabs on other people's territory such as spy satellites and surveillance flights as well as human agents - means that nobody else could muster.