Everything in the current US inventory has that property. The US didn't achieve that until 1960 or so, after extensive nuclear testing. It's not clear about the weapons of other nations.
The Hiroshima enriched uranium bomb was about as safe as an IED. It would have gone off if it hit the ground hard or was in a fire. The bomber crew had orders to dump the bomb in deep water if they had to abort the mission and return to base. Landing on Tinian with the bomb was considered far too risky.
The Hiroshima enriched uranium bomb was about as safe as an IED. It would have gone off if it hit the ground hard or was in a fire. The bomber crew had orders to dump the bomb in deep water if they had to abort the mission and return to base. Landing on Tinian with the bomb was considered far too risky.