Come up with a situation, as early in history as possible, with a stand off between any two (or three) countries having nuclear weapons-equipped satellites with missiles pointed at each others' countries.
First, you have to get nuclear weapons in orbit, and that's really hard. There's not really much point to putting bombs in orbit: they're expensive, they're vulnerable to attack, and only a small portion of them would be in position to attack at any given moment. There's a good reason they weren't deployed IOTL. The only real us they have is as a zero-warning first-strike weapon, cutting the warning time for attack to five minutes or less - but you can get almost as good a reduction using depressed-trajectory SLBMs. So why bother?
putting up something like this, which even with Energia or Saturn V rockets, isn't going to be possible until the 1970s, would certainly trigger a Cuban Missile type crisis
Depending on whether the ABM and Outer Space treaties existed, would almost certainly be considered by either side was a measure just short of war and indeed might even be considered the first overt act of such.