Captured documents reveal Russia's plan to annex Ukraine in ten days and kill its leaders

[erronis]

12. The US and other intelligence agencies were very sure of the Kremlin's plans;

they were warning Ukraine well before the invasion. If there was such a planning document it was probably in the IC's possession from early on.

I doubt that the Kremlin's intelligence services have been buttoned up any better since the invasion began. If anything the leaks and cooperation with the west have likely increased. It doesn't take a KGB agent to understand that things are not going to get better under Putin. Better to have some good creds with the outside in case ones life becomes untenable.