What is the Doctor's relationship with UNIT, and how has it evolved over the course of the show?

The Doctor's relationship with UNIT (United Nations Intelligence Taskforce) has been a long-standing part of the Doctor Who series, dating back to the Second Doctor's era in the late 1960s. UNIT is a military organization that fights extraterrestrial threats to Earth, and the Doctor has worked with them on many occasions to save the planet from various dangers.

Over the course of the show, the Doctor's relationship with UNIT has evolved and changed. In the classic series, the Doctor was a scientific advisor to UNIT, and he worked with them closely on many missions. However, in the new series, the Doctor has been more of an independent agent, working with UNIT when he needs to but also going off on his own adventures.

Despite these changes, the Doctor's connection to UNIT remains strong. He has worked with many of their agents over the years, including Brigadier Lethbridge-Stewart, who was a recurring character in the classic series. In the new series, the Doctor has worked with his former companion Martha Jones, who is now a high-ranking UNIT officer.

The Doctor's relationship with UNIT is a key part of the show's history, and it has played a significant role in many episodes over the years. Whether he's working closely with them or operating independently, the Doctor always has a deep respect for the men and women of UNIT who put their lives on the line to protect the planet.