- "Our mission went from recon to rescue the minute we found US soldiers butchered."
- — Martin Walker.
Martin Walker is the main protagonist and the true main antagonist of Spec Ops: The Line and the playable character.
He is a member of the United States Army's Delta Force. He and his squad are tasked with searching for any survivors left in Dubai, after receiving a message from Colonel John Konrad detailing his failed attempt at evacuating the city. Walker shows great respect for Konrad and expresses strong feelings of trust towards him throughout the game.
As the game progresses, Walker's mental stability slowly begins to deteriorate under the psychological strain caused by the repeated atrocities he and his squad are responsible for committing.
| Spoiler warning!|
The following section contains details about the plot or ending.
There are four possible conclusions regarding Walker's fate.
- The first is that he commits suicide after not being able to cope with the crushing reality of his actions in Dubai.
- The second is that he is killed by Falcon One, the army squad sent to rescue him, when he chooses to retaliate against them.
- The third is that he kills all of Falcon One, and continues to live in the ruined city of Dubai.
- The last is that he surrenders to Falcon One and is safely returned home, albeit mentally scarred.
- Walker's life was saved by Konrad during a mission in Kabul. This heavily influences Walker's feelings toward Konrad.
- In nearly all cutscenes in the game, Walker is shown using an M4A1. If Walker has 2 other guns, he will still be depicted with the M4A1 in cutscenes, which will change back into the equipped weapon once the cutscene ends. The only exceptions are in the scene before Delta rescues Rick Gould or two civilians, in which Walker uses a Scout Tactical, and the epilogue, where he uses an AA-12.
- Walker was originally going to appear much younger, with longer hair and a headband. His appearance however was changed at some point during development.
- As Walker degrades both physically and mentally throughout the course of the game, his language will shift from reserved and professional, to emotional and angry. His executions of enemies will also become more brutal.
- Walt Williams, the game's lead writer, personally believes that the helicopter crash during the sandstorm actually killed Walker and that the rest of the game is his Purgatory.