Unfortunately it's been a long time since I learned about BGP, if anyone could help out here I'd be grateful.
(And if they decide they don't care about plausible deniability, they could use sub-deployed timed mines to take out every cable at once.)
In an actual war, you hit the repair equipment and personnel [1].
(As to the Geneva Conventions note, we're discussing a hypothetical war with Russia. The status quo, including rules of war, are going to be rewritten by the victors.)
The frustrating part of this kind of petty tactic is that bullies can do just enough to annoy and inconvenience their targets, while never quite doing enough to make it worth expending the political capital to hold them to account. From the bully's perspective there's no downside. And if legitimate accidents or rogue actions get portrayed as deliberate then all the better - that just reinforces the bully's reputation as an actor to be feared while further eroding trust in the international institutions that may one day challenge it.
It's pretty cool tech
To be clear, I’m saying to terminate each end of the cut cable to a terminating device that continues the flow of light, not just the termination at the beginning/end of the line. Sorry if that wasn’t obvious.
"Sabatoge" and repair is discussed at 11:45