Nuclear war

A nuclear war was a war in which nuclear weapons were used. On the worlds on which they were fought, they usually resulted in making the planet mostly or completely uninhabitable.

Nuclear wars on Earth

 * For more details, see World War III.

In an alternate timeline, it is thought that John F. Kennedy would have started a nuclear war. (MA: Who Killed Kennedy)

Nuclear wars on other worlds
On Skaro, the Thousand Year War (and the neutronic war, if they were separate conflicts) was fought with nuclear weapons as well as chemical and biological arms. The result was massive deaths and mutations that eventually led to the creation of the Daleks. (DW: Genesis of the Daleks, The Daleks)

The planet Minyos was rendered uninhabitable by nuclear war, which had been indirectly caused by the Time Lords. (DW: Underworld)

Atrios and Zeos were engaged in nuclear war for five years. (DW: The Armageddon Factor)

The planet Argolis was made uninhabitable and the Argolins made sterile after a twenty-minute nuclear war with the Foamasi. (DW: The Leisure Hive)

The Panjistri told the Kirithons that the original inhabitants of Kirith had destroyed themselves in a nuclear war, leaving only their ruins behind; this, like everything else the Panjistri told them, was a lie. (NA: Timewyrm: Apocalypse)

The civilisation of one unnamed world destroyed itself in a nuclear war after a group of Eternals, for their own amusement, posed as gods and gave them knowledge of atomic power. Afterwards, they held a party in the ruins. (DWM: Uninvited Guest)