Land, Air, Sea nuclear capability
So the means typically
Sea: Subs, Carriers
Air: Planes drop nukes or fire nuclear tipped missiles
Land: Silos, or mobile ICBM's.
They took out 36% of their air capability
Apparently one of their subs got hit (and/or a sub port)
That's hitting 2/3rd of their triad, including a huge portion of one of them.
This alone... can justify a nuclear strike by doctrine.
If you lose your ability to fight a nuclear war, one can be waged against you.
So keeping that from being taken out, is a rationale to launching a nuclear war.
Ukraine just fucked around and triggered that.
Doesn't mean it will happen.
It means, they're playing a dangerous game
Now they're still doing strikes.
Plus they took out a bridge just before these strikes.
Whatever the response is, it's gotta be massive.
The world will be lucky if they launch a bunch of kalibers/iskanders/oerskhin (sp) at them, plus a fleet of doritos, plus push on every front....
....and then drop some of their biggest if not biggest thermobarics on population centers.
Which are basically small non-nuke nukes.