- This level occupies the map slot E1M9. For other maps which occupy this slot, see Category:E1M9.
- This level occupies the map slot MAP56. For other maps which occupy this slot, see Category:MAP56.
- This level occupies the map slot MAP24. For other maps which occupy this slot, see Category:MAP24.
- This level occupies the map slot MAP17. For other maps which occupy this slot, see Category:MAP17.
- This level occupies the map slot E1M8. For other maps which occupy this slot, see Category:E1M8.
E1M9: Military Base (MAP56 in PSX/Saturn, MAP24 in Jaguar/3DO/GBA, MAP17 in 32X, E1M8 in SNES) is the secret map of Knee-Deep in the Dead in Doom, which can be accessed from E1M3: Toxin Refinery. It was designed by John Romero and uses the music track "Hiding the Secrets". The par time is 2:45.
Completing this level takes the player to E1M4: Command Control.
- Letters in italics refer to marked spots on the map. Sector numbers in boldface are secrets which count toward the end-of-level tally.
You begin in a short corridor; at the end of this corridor is a large courtyard (A) containing Imps in a cage. Go down the stairs to the west and get the yellow key behind the fence (B). Return to the courtyard and go down the stairs to the east. Turn right, open the yellow door, and pick up the red key (C). Leave the room through the other yellow door, continue west through a room with a large "box" pillar surrounded by four torches, and go down the stairs and through the red door. Cross to the far wall of that room and turn left; you should see a switch behind a row of barrels (D). Shoot the barrels from a safe distance and press the switch. This raises the "box" pillar in the previous room to reveal the blue key (E). Get the blue key, then return to the central courtyard and go down the stairs to the north. Behind the blue door is the exit room; the exit switch is visible across a nukage canal, but inaccessible (F). Jump into the canal and follow it around (in either direction) to a platform (G) with a green switch and an Imp. When you step onto the platform, a passage will open behind you (H). Click the switch, then enter the passage. Follow it to a lift (I), and go through the hidden door at the top of the lift. You will now see a wide bridge across the canal. Cross the bridge and activate the exit switch.
Other points of interest
If you are starting this level from scratch, the sergeants in the central courtyard (four on Hurt me plenty, eight on Ultra-Violence and Nightmare!) may cause you a lot of trouble. Stay as far away from the courtyard as possible until you kill a sergeant very close to the short corridor, then grab his shotgun. Alternatively, as soon as you have killed the zombies emerging from the south staircase, run down that staircase and get the chaingun (see secret #1 below).
To the north of the yellow key room is a room containing a rocket launcher (J). When you step onto the red star, however, a pack of monsters will begin teleporting into the room. There is a large number of demons that the player has to fight, while there is little or no reward ammo or health packs afterward, so this will considerably weaken the player's offensive and defensive capabilities.
In the room east of the central courtyard, the brightly lit area along the east wall is really a lift (K). This brings you to an outdoor area containing three tall pillars with Imps on top, as well as a medikit and a green armor. Crossing to the powerups will cause the pillars to lower.
Taking the red key opens a trap in the southeast wall of the room (L), revealing additional monsters and health pickups. With great care, it is possible to pick up the key without triggering the trap.
The switch that reveals the blue key also opens a second passage (M) back to the previous room (on the south wall, behind some other barrels). It contains a medikit, a bullet box, and a shell box. The blue key is guarded by two Demons (I'm too young to die and Hey, not too rough), or six Demons (HMP), or eight Demons (UV and NM).
When you step onto the platform in the nukage canal, an Imp (ITYTD and HNTR), or three Imps (HMP), or four Imps (UV and NM), will be released as the new passage opens. At the same time, a trap opens next to the exit switch (N), releasing a Spectre (ITYTD and HNTR) or three Spectres (HMP, UV, and NM); watch out for these as you re-enter the exit room, since they may cross the bridge immediately.
The map of E1M9 can remind one of an abstract visualization of a right-facing swastika .
- In the room east of the central courtyard, a hidden lift in the southwest corner (O) drops down into a nukage pool. In the room south of the central courtyard, a hidden lift in the northeast corner (P) drops down into the same nukage pool. You can get a chaingun and a large number of bullets there. (sector 65)
- In the exit room, there is a secret door in the center of the east wall, indicated by a different texture. Behind this door (sector 20) is a room with items atop pillars (Q), including a backpack, a chainsaw, and several large ammo pickups. As you reach the bottom of the staircase, a lift will drop near the far wall, allowing you to ride to the top of the tallest pillar. To collect the items, jump carefully from pillar to pillar: back up as far as you can without falling off, run toward the next pillar, then stop quickly as you land. If you make a mistake, just return to the steps to lower the lift again. It is easiest to go around the pillars counterclockwise, from highest to lowest.
The blockmap bug sometimes occurs in the short corridor where the player starts.
Entering the southern area of the yellow key room may awaken an Imp (Thing 52) in the room to the south, even though there is a locked door between you. This is an instance of the "sleepwalking sergeant" bug: the Imp is at (-576,-960) and one of the linedefs on the staircase is at y = -576.
The ceiling of the platform in the nukage canal is high enough that the switch texture tiles twice vertically. It is possible to see the bottom part of the second switch when approaching the platform from the north.
- No monsters, 100% secrets walkthrough (file info)
- 100% kills, items, and secrets on ITYTD (file info)
- 100% kills, items, and secrets on HNTR (file info)
- 100% kills, items, and secrets on HMP (file info)
- 100% kills, items, and secrets on UV (file info)
Areas / screenshots
Routes and tricks
The shortest route through this map is to enter and leave the red key room through the west door. Some luck is required to survive a straight speedrun: the group of sergeants in the red key room often inflicts a large amount of damage, and the Demons guarding the blue key can easily surround you (especially if you kill only one or two with barrel frags).
The switch that reveals the blue key can be pressed without destroying the barrels.
When playing on NM, most players make a detour either to the chaingun or the rocket launcher, in order to clear paths through crowds more quickly. The second method is more dangerous, since it releases fifteen extra monsters, but faster, since the rocket launcher is so powerful. 
For styles requiring 100% kills, the most efficient approach is to ignore the monsters in the central courtyard, then run in and out of the rocket launcher room after getting the yellow key. By the time you clear the red key room, most of these monsters will have collected at the foot of the staircase to your west. (Because of the open layout of the level, however, this may backfire as monsters wander up to the central courtyard and enter other rooms.) Anders Johnsen credits Yonatan Donner with inventing this route.  
A small amount of time can sometimes be saved in the exit room by not killing anyone until the bridge is raised. With luck, the Spectres will gather near you as you emerge from the lift, and some will be damaged by the Imps and sergeants (and therefore not attack you right away).
In NM100S, the fastest way to reach secret #2 is to jump across the nukage canal, shoot the deaf Spectres with rockets, then jump back across the canal to the secret door. If you are out of rockets, you can instead run through the secret door immediately, so that only one Spectre approaches you at a time. For an episode run, the extra rockets in secret #2 and the extra bullets in secret #1 are both good investments. 
A small amount of time can be saved in UV -fast mode by approaching the blue key through the south passage, then firing into the room between the barrels. Zombies will often enter from the central courtyard and start infighting with the Demons. (This is dangerous, since a stray pellet may cause the barrels to explode.) In episode runs, secret #2 is sometimes entered fully in order to restock on rockets.
Due to the number of Demons and Spectres on this level, UV Tyson runs are fastest when the chainsaw is obtained quickly (clearing only the red key room and the room with the blue key switch). The green armor is important for surviving all the way to secret #2.
The Compet-N records for the map are:
|UV speed||00:29||Vincent Catalaá||1999-10-30||e1m9-029.zip|
|NM speed||00:46||Drew "stx-Vile" DeVore||2001-11-16||n1m9-046.zip|
|UV max||02:16||Drew "stx-Vile" DeVore||2002-07-30||e1m9-216.zip|
|NM100S||01:02||Drew "stx-Vile" DeVore||2002-05-12||n1s9-102.zip|
|UV -fast||02:54||Anders Johnsen||2000-03-07||f1m9-254.zip|
|UV -respawn||02:07||Mate "Relic" Crncevic||2013-08-17||r1m9-207.zip|
|UV Tyson||04:36||Radek Pecka||2002-11-20||t1m9-436.zip|
|UV pacifist||00:33||Selim "Bastard" Benabdelkhalek||2004-02-04||p1m9-033.zip|
|Monsters||ITYTD and HNTR||HMP||UV and NM|
|Powerups||ITYTD and HNTR||HMP||UV and NM|
|Weapons||ITYTD and HNTR||HMP||UV and NM|
|Ammunition||ITYTD and HNTR||HMP||UV and NM|
|Keys||ITYTD and HNTR||HMP||UV and NM|
|Barrels||ITYTD and HNTR||HMP||UV and NM|
- This is the only level in Episode 1 that features a monster teleport.
- This level is called "The Military Base" in the Playstation version.
- In version 1.0 of the game, locked door messages on this level say that you need a Skull key, rather than a keycard.
- The music for this level is inspired by "Down in the Sewer" by The Stranglers.