At 'Game Options' select 'Yes' for the Game Console. Then during the game press the '~' (tilde) key to bring the console up and type the following codes (without the quotes) to play the corresponding level.

Play 'Eviction' Mission:
Devmap ber2

Play 'Semper Fi' Mission:
Type 'Devmap mak'

Play 'Little Resistance' Mission:
Type 'Devmap pel1'

Play 'Their Land, Their Blood' Mission:
Type 'Devmap see1'

Play 'Hard Landing' Mission:
Type 'Devmap pel2'

Play 'Relentless' Mission:
Type 'Devmap pel1b'

Play 'Ring Of Steel' Mission:
Type 'Devmap ber1'

Play 'Vendetta' Mission:
Type 'Devmap sniper'

Play 'Blood and Iron' Mission:
Type 'Devmap see2'

Play 'Burn 'Em Out' Mission:
Type 'Devmap pel1a'

When you reach the indicated level the corresponding Perk slot features will become available.

Perk Slot 1

Unlock Satchel Charge x2:
Reach Level 4 (2 remote detonation explosives).

Unlock Special Grenade x3:
Reach Level 4 (3 special grenades, no smoke).

Unlock M9A1 Bazooka x2:
Reach Level 4 (bazooka with 2 rockets).

Unlock Bomb Squad:
Reach Level 16.

Unlock Bouncing Betty x2:
Reach Level 24.

Unlock Bandolier:
Reach Level 40.

Unlock Primary Grenade x2:
Reach Level 44.

Unlock M2 Flamethrower:
Reach Level 65.


Perk Slot 2

Unlock Juggernaut:
Reach Level 4 (increased health).

Unlock Stopping Power:
Reach Level 4 (increased bullet damage).

Unlock Flak Jacket:
Reach Level 4 (reduce explosive damage).

Unlock Gas Mask:
Reach Level 4 (protect against Tabun Gas).

Unlock Fireworks:
Reach Level 4 (higher explosive weapon damage).

Unlock Camouflage:
Reach Level 12.

Unlock Sleight Of Hand:
Reach Level 28.

Unlock Shades:
Reach Level 32.

Unlock Double Tap:
Reach Level 36.

Unlock Overkill:
Reach Level 56.


Perk Slot 3

Unlock Deep Impact:
Reach Level 4 (deeper bullet penetration).

Unlock Extreme Conditioning:
Reach Level 4 (sprint for longer distances).

Unlock Steady Aim:
Reach Level 4 (increased hip fire accuracy).

Unlock Toss back:
Reach Level 6 (reset fuse of picked up grenades).

Unlock Second Chance:
Reach Level 9 (revive downed allies).

Unlock Martyrdom:
Reach Level 20.

Unlock Fireproof:
Reach Level 48.

Unlock Dead Silence:
Reach Level 52.

Unlock Iron Lungs:
Reach Level 60.

Unlock Reconnaissance:
Reach Level 64.


Vehicle Perks

Unlock Greased Bearings:
Reach Level 4 (increased turret rotation speed).

Unlock Water Cooler:
Reach Level 4 (decreased turret overheat).

Unlock Ordnance Training:
Reach Level 12.

Unlock Lead Foot:
Reach Level 28.

Unlock Coaxial Machine Gun:
Reach Level 40.

The following list of weapons and weapon attachments can be obtained by completing the corresponding task.

Rifles

Unlock SVT-40:
Reach Level 4.

Unlock Gewehr 43:
Reach Level 7.

Unlock M1 Garand:
Reach Level 17.

Unlock STG-44:
Reach Level 37.

Unlock M1A1 Carbine:
Reach Level 65.

Unlock Flash Hider:
Complete Marksman Challenge 1 (invisible on radar when firing, reduced muzzle flash, but shorter range).

Unlock Suppressor:
Complete Marksman Challenge 1 (invisible on radar when firing, reduced muzzle flash, but shorter range).

Unlock Aperture Sight:
Complete Marksman Challenge 2 (precision sight).

Unlock Telescopic Sight:
Complete Marksman Challenge 3 (enhanced telescopic sight).

Unlock Rifle Grenade:
Complete Marksman Challenge 4 (grenade launcher attachment, replaces Perk 1 slot).


Bolt Action Rifles

Unlock Springfield:
Reach Level 4.

Unlock Arisaka::
Reach Level 4.

Unlock Mosin-Nagant:
Reach Level 21.

Unlock Kar98k:
Reach Level 41.

Unlock PTRS-41:
Reach Level 57.

Unlock Sniper Scope:
Complete Marksman Challenge 1 (accuracy and range increases).

Unlock Bayonet:
Complete Marksman Challenge 1 (melee attack range increases).

Unlock Bayonet:
Complete Marksman Challenge 2 (melee attack range increases).

Unlock Rifle Grenade:
Complete Marksman Challenge 2 (grenade launcher attachment, replaces Perk 1 slot).

Unlock Rifle Grenade:
Complete Marksman Challenge 3 (grenade launcher attachment, replaces Perk 1 slot).


Machine Guns

Unlock Type 99:
Reach Level 4.

Unlock BAR:
Reach Level 4.

Unlock DP-28:
Reach Level 13.

Unlock MG 42:
Reach Level 33.

Unlock FG 42:
Reach Level 45.

Unlock Browning M1919:
Reach Level 61.

Unlock Bipod:
Complete Marksman Challenge 1 (reduces motion for more accuracy).


Sub Machine Guns

Unlock Thompson:
Reach Level 4.

Unlock MP40:
Reach Level 10

Unlock Type 100:
Reach Level 25.

Unlock Ppsh:
Reach Level 41.

Unlock Suppressor:
Complete Marksman Challenge 1 (invisible on radar when firing, reduced muzzle flash, but shorter range).

Unlock Aperture Sight:
Complete Marksman Challenge 2 (precision sight).

Unlock Round Drum:
Complete Marksman Challenge 3 (increased ammunition capacity).

Unlock Dual Magazine:
Complete Marksman Challenge 3 (increased ammunition capacity).


Shotguns

Unlock M1897 Trench Gun:
Reach Level 4.

Unlock Double Barreled Shotgun:
Reach Level 29.

Unlock Grip:
Complete Marksman Challenge 1 (vertical foregrip to reduce recoil, replaces Perk slot 1).


Pistols

Unlock Colt M1911:
Reach Level 4.

Unlock Nambu:
Reach Level 4.

Unlock Walther P38:
Reach Level 4.

Unlock Tokrev TT-33:
Reach Level 21.

Unlock .357 Magnum:
Reach Level 49.


Primary Grenades

Unlock Frag:
Reach Level 4.

Unlock N 74 ST:
Reach Level 4.

Unlock Molotov Cocktail:
Reach Level 10.


Special Grenades

Unlock Smoke Grenade:
Reach Level 4.

Unlock Tabun Gas Grenade:
Reach Level 4.

Unlock Signal Flare Grenade:
Reach Level 4.


Extra custom Weapon Slots
When you reach the indicated Prestige rank the corresponding extra custom weapon slot will become available.

Unlock Slot 6:
Reach 1st Prestige.

Unlock Slot 7:
Reach 2nd Prestige.

Unlock Slot 8:
Reach 4th Prestige.

Unlock Slot 9:
Reach 7th Prestige.

Unlock Slot 10:
Reach 10th Prestige.

The following features become available options when the indicated task has been completed.

Unlock Veteran Mode:
Veteran mode becomes unlocked when you reach Level 32. This feature is a Co-Op mode with enemies that are harder to defeat.

Unlock Zombie Mode:
Complete Campaign mode to unlock this feature which is a 4-Player Co-Op mode with endless waves of Nazi zombies attacking you.

If you need help in this game press the '~' (tilde) key during gameplay to display the console window and then type 'devmap mak' and press 'Enter'. Doing this will enable 'Cheat' mode allowing you to type the following codes (without the quotes) to activate the corresponding effect.

Unlock God Mode:
Type 'god'

Unlock ALL Weapons:
Type 'give all'

List Maps:
Type 'mapname'

Change Maps:
Type 'devmap (map name)'

Disable AI:
Type 'notarget'

No clipping Mode:
Type 'noclip'