Monk invasion

The Monk invasion of Earth lasted for a period of just over six months, during which the people of Earth were brainwashed into believing an alternate history in which the benevolent Monks had both guided human evolution and guarded them from threats as powerful as the Daleks, Cybermen and Weeping Angels.

Preparing to invade
To prepare for the invasion, the Monks used a simulation known as the Shadow World to track humans and to choose the right moment to invade. The simulated Twelfth Doctor used his sonic sunglasses to send an email of his experiences to his real self. (TV: Extremis)

Awaiting consent
Having identified the release of Raoultella planticola at Agrofuel Research Operations as the beginning of a world-ending catastrophe, the Monks landed the Cathedral in the centre of a warzone in Turmezistan. They set every clock on the world to count down to the planet's destruction and, after a failed attempt to destroy the Cathedral, they asked the Twelfth Doctor, Bill Potts, Nardole, the Secretary General, Colonel Brabbit, General Xiaolian and General Svyatoslavovich for their consent to occupy Earth and avert the catastrophe.

The Monks disintegrated the Secretary General when he offered his consent out of fear and later killed Brabbit, Xiaolian and Svyatoslavovich when they offered their consent out of strategy. The Doctor worked with Erica to prevent the release of Raoultella planticola and created a bomb to wipe it out, but he was stuck inside with it and, being blind, he could not get out. To restore his sight and save him, Bill gave the Monks her consent. (TV: The Pyramid at the End of the World)

The reign of the Monks
With Bill's consent, the Monks moved the Cathedral to London and and erected statues of themselves in every major city to transmit their True History with Bill's brainwaves. They reinforced this by having the Doctor make broadcasts in support of the Monks and had the Memory Police arrest those who could remember what really happened. Six months after the invasion, Bill and Nardole found the Doctor and returned with him to St Luke's University to speak with and find out how to defeat the Monks.

The Doctor refused to leave Bill brain-dead as Missy suggested and tried to hack into the transmitter to broadcast the real history of Earth without success. Bill took over and, whilst at first the Monk used her to strengthen their hold over Earth, her imagined memories of her mother were uncorrupted and broke their hold. The Monks then evacuated in the Cathedral and erased themselves from the humans' memories. (TV: The Lie of the Land)