The ground had been changing for an hour before the signal came.
The steppe's dry hardness was giving way beneath the horses' feet, the soil darkening in patches where moisture worked up from channels below. Reed beds had appeared to the east of the march route an hour back, running in long dense lines that broke the flat horizon into sections.
Coming off the open channels was a smell different from the Caspian's mineral cold, standing water, mud, a cultivated region somewhere further south. The delta was close enough to be in the air before it was in sight.
Batu had been watching the terrain change as the tumen moved through it. The reed beds were cover. Dense enough to conceal riders. Tall enough to take a man in three strides.
The channels between them provided withdrawal routes that a pursuing force would have to know in advance to block, and the channels were not on any felt map the army carried.
