Vlad Tepes often had the stakes arranged in various geometric patterns. The most common pattern was a ring of concentric circles in the outskirts of a city that was his target. The height of the spear indicated the rank of the victim. The decaying corpses were often left up for months. It was once reported that an invading Turkish army turned back in fright when it encountered thousands of rotting corpses impaled on the banks of the Danube. In 1461 Mohammed II, the conqueror of Constantinople, a man not noted for his squeamishness, returned to Constantinople after being sickened by the sight of twenty thousand impaled Turkish prisoners outside of the city of Tirgoviste. This gruesome sight is remembered in history as "the Forest of the Impaled."
Well, he made his point, I suppose.
This is not an army, exactly, is it?
This will take a different skill set.