From Merlin...

Everyone is familiar with the Trinity Hellstorm and the Antarctic Hellstorm.

That's what happens when you try to induce nuclear fission.  Both cases a sub-critical mass was used and a

What everyone forgot was that fission had occurred naturally in several places before Oppenheimer's "little cantrip."

Everyone except the increasingly desperate people of Rhodesia in 1975.

They knew they were losing their war for independence when South Africa started turning its back on them.  They needed something dramatic to turn the tide.

They found it.

They'd become very adept at smuggling in small arms and other military material.  They discovered that smuggling one thing was much the same as anything.

What they smuggled was yellow-cake uranium.  The hope was to build a NEMA reactor to make better material for the war effort.  What went wrong was the spell they were using for purifying the uranium did not account for keeping the now critical mass separated from itself.  The mass went critical, but did not create a new hellstorm.  What Rhodesia got was a typical reactor's weakening of the walls of reality, but this time it was a gateway to another world.

A world much like our own, in fact.  The first weakening that did not cause an influx of demons.  Suddenly who controlled Rhodesia mattered a great deal to the first world powers.  The United States flush with its recent victory in Vietnam, stepped in to support the break-away colony; provided that a path to majority rule be established.

By 1987 the bush wars had finally ended and by 1990 the first election by the full population had occurred.  That vote confirmed the previous policies of Rhodesia and began putting pressure on South Africa to follow suit.  Rhodesia became a shining example of post colonial Africa where the decendents of both Europe and Africa would live and work together harmoniously.

The darker history is what was happening on the other side of the gateway from 1978 through 1989...