First unlock the game's console by going to Game Options and select "Yes" for the Game Console. Next open it up with the ~ key. Then, type in these codes to go to the level.

Password	Effect
Devmap see2	Play the mission Blood and Iron
Devmap pel1a	Play the mission Burn 'Em Out
Devmap ber2	Play the mission Eviction
Devmap pel2	Play the mission Hard Landing
Devmap pel1	Play the mission Little Resistance
Devmap pel1b	Play the mission Relentless
Devmap ber1	Play the mission Ring Of Steel
Devmap mak	Play the mission Semper Fi
Devmap see1	Play the mission Their Land, Their Blood
Devmap sniper	Play the mission Vendetta