In the 2011 film Transformers: Dark of the Moon, the character referred to as Colonel is Colonel William Lennox. He is a high-ranking officer in the United States Army and a seasoned veteran of the conflict between the Autobots and Decepticons. By the time of the film's events, he has been promoted from the rank of captain seen in earlier conflicts, reflecting his growing experience and leadership in the clandestine war against the Decepticons.

Lennox is characterized as a capable, brave, and loyal soldier who maintains a professional yet personable demeanor. He is a family man, married to his wife Sarah and father to his daughter Annabelle, and his desire to protect his family and Earth is a driving force behind his actions. Despite the immense pressure of his duties, he remains level-headed, resourceful, and charismatic, earning the deep trust and respect of the men and women under his command as well as his Autobot allies. He is portrayed as a man of action who is not easily rattled, even when facing overwhelming odds.

As the field commander of NEST, the international military task force created to partner with the Autobots, Lennox's primary motivation is to neutralize the Decepticon threat. He is deeply committed to the alliance with Optimus Prime and his team, seeing them as crucial partners in ensuring global security. His role in the story is central to the human military response. He leads his troops on key missions, including a critical investigation in Chernobyl, Ukraine, where the remains of a Cybertronian spacecraft are discovered. This mission sets off the chain of events that reveals the Decepticons' grand scheme involving the Autobot leader Sentinel Prime. Throughout the escalating crisis, Lennox acts as a key liaison and tactical coordinator, directing his soldiers in the final, devastating battle for Chicago.

Lennox shares key relationships with several individuals. He has a long-standing brotherhood with Sergeant Robert Epps, a fellow NEST operative who has fought alongside him since the earliest battles. He is a trusted ally and friend to Optimus Prime and the Autobots, working seamlessly with them in combat. He also maintains a connection with Sam Witwicky, a civilian who has repeatedly been at the center of the Transformers war, recognizing Sam's value despite his non-military status. A significant new dynamic is his working relationship with Director Charlotte Mearing, a high-ranking government official who oversees NEST, requiring Lennox to navigate political pressures while focusing on tactical objectives.

Over the course of the film series, Lennox undergoes clear professional development, rising from a captain in the first film to a colonel by the third, solidifying his position as the human race's primary military commander in the fight against the Decepticons. His personal development is reflected in his unshakeable resolve and the heavy burden of command he carries, having evolved from a soldier trying to get home to his newborn daughter to a global leader responsible for coordinating humanity's defense. In Dark of the Moon, his authority is fully established, and he operates as a decisive strategic leader on the world stage.

Regarding notable abilities, Colonel Lennox is a highly trained and decorated United States Army Ranger. He is an expert in tactical planning, field command, and urban warfare. He is proficient with a wide array of military weaponry and is a skilled combat leader, capable of making split-second, life-or-death decisions under fire. His greatest ability, however, is his strategic leadership and his effectiveness in coordinating human military forces alongside Autobot warriors, showcasing a unique proficiency in joint, interspecies combat operations.