Many articles posted.
In the fwiw department, the Ukes could have nukes in about 6 months. The U235, the knowledge, chemistry, and machining abilities to do it. Not sure of delivery capacity.
Problem is testing it.
If Japan so chooses to go nuclear, it would take less than six weeks to have a deliverable weapon. They would have to test it.
It would be a good idea if all parties called a ceasefire in place.
5.56mm
As my brother unfortunately once reminded me, the nuclear bomb is 1940’s technology! The problem is refining the uranium, not the technology.