21st century Martian invasion of Earth
It should be relocated at Ice Warrior invasion of Earth (The Seeds of Death) because They're the same subject.
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An invasion of Earth was attempted by the Ice Warriors in the 21st century. (TV: The Seeds of Death)
During his trial, the Second Doctor recalled via a Thought Channel the Ice Warriors' invasion of Earth as one of the "evils" he had broken the Time Lord code of non-interference to fight. (TV: The War Games)
The Keller Machine used the Third Doctor's memory of Slaar to attack him. (TV: The Mind of Evil)