The Doctor went to war with the Cybermen on Mondas for two episodes, but the mission and the journeys prior have taken their toll.
The Doctor was forced to rest in the third act, but ultimately regained consciousness and played a part in protecting Earth from the wrath of the Cybermen.
This story was later expanded upon in the 2017 Christmas special “Twice Upon A Time,” but we’ll get into that a little later.
Unfortunately, he was far too weary and retreated to the TARDIS knowing his time is up.