President Joe Biden has given permission to Ukraine to strike inside Russian territory with American munitions, though he has restricted their use so Kyiv can only hit targets over the border close to Kharkiv after Russia made significant advances around the city in the northeastern part of the coun...
This is the Western version of the salami slice method. A bit more weapons. Russia blathers about retribution and consequences, maybe another salvo and that's it. Give longer range weapons and check reaction from Russia. Allow targeting Russia but limited. Now countries are slowly talking about training in Ukraine and boots on the ground and getting the classic consequences speech from Russia.
Today they have something like 7 minutes to decide whether to launch a retaliatory strike if missiles are en route if recall correctly, 12 hours seems like a luxury.
I think the 12 hours are in reference to a conventional invasion. In case of a nuclear attack the decision might not even be made by someone high-up on account of them being encased in glass but by the crew of the nuclear subs, based on a letter the higher-ups left for that circumstance.