Slip away from the sight of the horde and hide within the ruins. My battlebrothers and I would all be devastators wielding lascannons along the top floor of one side of a ruined structure. As soon as the Chaos Lord struts through at a typical meandering pace we would focus-fire his back side with red dots and completely obliterate him along with any other high-priority targets. Not only would guerilla warfare such as this buy time for reinforcements to arrive, it would allow us to strike our enemy fiercely while their guard is down.
Check my ammo on my storm bolter and Mag lock my battle hammer to my waist. Grab my Battle shield, and say a latany of battle to the God Emperor of Mankind and to the primarch Roboute Guilliman, Check my Battle brothers, Give them the battle Cant to form a Battle wedge, And march 3 strong in our Terminator battle armor.
Joke's on the Space Marine - that CSM is a follower of Slaanesh... His god is all too present in that image.
When you are the last to hold the line, you trust in the God Emperor and your Primarch to Protect the Angles that stand there ground. The Chaos Filth will not advance any farther and defile the land we are sent to protect. We will protect the innocent at all costs and stop the flow of chaos. My Battle brothers and I will not let this taint go unabated, we will show no mercy for the Heretic and set them alight with Holy Promethium.
Many graves have been filled by imperial fools that believed that bellowing to their Corpse God would somehow save them from overwhelming odds. Good to see the propaganda is working.
if you ask me i would charge forth screaming FOR THE LION!!!!!! as i smash into the enemy line with my thunder hammer and start smashing my way threw till finally i stand before the chaos lord and challenge him to one on one combat which usally they must accept as my battle brothers fight the demons that stand around us till reinforcements came or the lord was crushed under the boot of the god emperors angels of death.
Running away leads to a cowards death, face down in the ashes of the world they failed to protect, their backs pockmarked from enemy fire. That is no death for me.