It may be the that your chances of returning to Imperial lines are too slim to contemplate. If this is the case sell your life dearly. Do not be found whimpering in a hole, to be dragged by the whooping horde and paraded like a trophy! The Emperor will frown on such an ignominious end to a soldier in His army. Do not disappoint Him!
Use your untenable situation to your advantage. You may find yourself in the soft underbelly of the foe. Strike! Find a target. Set explosives. Kill sentries. Snipe officers. Strike and move. Strike and move. The Emperor will protect a man who is willing to sell his life dear! The more damage you do, the more fortune from the Emperor you will earn.
Gut the enemy from the inside. Spit in his eye. Show him what a Guardsman in peril is capable of. Earn your place seated by the Golden Throne.
— Behind Enemy Lines – Disrupt and Destroy,” The Imperial Infantryman’s Uplifting Primer, Chapter 3 Section 16, Warhammer 40,000