Durin had arrived near Marinka by the time he saw the city burning.
Looking at the swarms of green skin upon the earth, Durin ultimately had no choice but to turn around and leave—there was no fighting nearby, the city was burning, and there were no signs of resistance. The reason why the Green-skinned Orcs were called green skin was because they spread like a plague.
Wherever they went, they brought death.
On his journey westward, Durin encountered a fleeing group and descended to find the person in charge.
It was a wealthy man dressed in fur, who looked at Durin warily, "Mage sir, what do you need with me? As you can see, the green skins have broken through the defenses, and we're all fleeing to Zaporozhye."