WHAT DOES UNDERWATER NUCLEAR TEST 'UMBRELLA' MEAN?

With test moratoriums on the horizon, American weapons labs rushed out lots of new patterns. A hard deadline for testing was established at midnight (0000 hrs), 31 Oct 1958, as negotiations were set to start out that working day, as well as program shows it, with 29 tests executed in October, 4 of them on the last working day. One other test was ca