- For a list of other Allens, see Allen.
- PFC. Joseph Allen: "So how do I look?"
- General Shepherd: "Like one of the bad guys."
- — PFC. Joseph Allen and General Shepherd.
Private First Class Joseph Allen (AKA Alexei Borodin) (Russian: Алексей Бородин) was a playable character and the main protagonist in the early part of Call of Duty: Modern Warfare 2. He is introduced in "S.S.D.D." helping Sergeant Foley train Afghan National Army troops at Firebase Phoenix in Afghanistan. He then undergoes a selection phase for Task Force 141, running "The Pit", prior to engaging local OpFor troops immediately after. He is then hand-picked by Shepherd to go undercover in Vladimir Makarov's cell under the alias Alexei Borodin. Allen was killed by Makarov when attempting to escape from Zakhaev International Airport in the level "No Russian", having learned about
his real identity. He became a victim of a conflict of goals between General Shepherd and Makarov. It is interesting to note that his voice is heard later in the game after he has been picked for Task Force 141, making him the one of the few playable characters in the Call of Duty series to be heard. Before joining the Rangers, he lived in Ithaca, NY.
- Firebase Phoenix, Afghanistan - Assisted in the training of local military forces, participated in combat operations IVO Firebase Phoenix.
- Zakhaev International Airport, Moscow - Participated in CIA-sponsored deep-cover infiltration of Makarov's inner circle; compromised and killed by Makarov.
- "It's an honor, Sir. When do I meet the rest of the team?"
- — Joseph Allen to Shepherd in the Cliffhanger cutscene
- The name Alexei Borodin might be a reference to the first Call of Duty game, because of the fact that the first playable Russian character's first name is Alexei, and the first person the player meets has the last name "Borodin".
- He is one of the only playable characters who speaks in the Modern Warfare series, the others being Cpt. Price, Soap and the AC-130 crew in Call of Duty 4.
- The tattoos on Allen's chest that were added as part of the operation are Russian Prison tattoos. The cathedral is symbolic of how long a person has been in prison, with each steeple representing a sentence.
- PFC. Allen was the fourth youngest playable character (after C. Miller and Aleksandr Sokolov, both 20, and Dimitri Petrenko, 18 at a time) and the youngest to die to date.
- He is one of the two playable characters in Modern Warfare series to be seen without gloves, the other being James Ramirez.
- Sometimes on Call Of Duty: Black Ops a random friendly NPC may spawn named Pvt. Allen