Tactical nukes aren’t real. They start an escalation ladder that gets you to global thermonuclear war in a few hours. Using a “tactical nuke” is just laying naked your intent to have things go nuclear while giving your opponent a chance to respond.
During the Cuban Missile Crisis Kennedy wanted to nuke Cuba. The joint chiefs told him that if he wanted to do that he would also have to nuke Russia in a massive fully committed first strike.
Not secret