In 2006, Earth's first interplanetary war was anticipated as the British government requested that the United Nations provide access codes for nuclear weapons against an alien threat. In reality, this was a Slitheen plot to destroy the Earth for profit, which was thwarted by the Ninth Doctor. (TV: World War Three)
Over the 50 years after sending a rocket to the planet Mechanus, Earth became involved in interplanetary wars, with Steven Taylor cited the Human-Draconian War, the Second Dalek War and the Third Dalek War as factors which put an end to Earth's expansionist phase, leaving planets like Mechanus uncolonised. (PROSE: The Chase)