Tricobalt satellite

From Memory Alpha, the free Star Trek reference

Tricobalt satellites were one of the computerized weapons employed by Vendikar during its five hundred year war with Eminiar VII. At the time of the Enterprise's visit in 2267, these weapons existed only in the data stores of the powerful computers that waged the war. Such a weapon "destroyed" the Enterprise while it orbited Eminiar, forcing Anan 7 to demand that Kirk beam his crew down so they could be killed and their deaths recorded in keeping with the treaty that governed the conduct of the war. (TOS: "A Taste of Armageddon")

Tricobalt is a TOS-style tech update of the much dreaded (at the time) cobalt bomb. The cobalt bomb, which was never built or tested, would have a 'slow burning nuclear yield' of immense radiation and toxicity, rendering an area lethal for an estimated five years or more. If the Vendikans were running simulations with a more powerful version of that weapon, it is no wonder the Eminians were afraid of a real war.