across full five miles of villages and fields and woods the battalions were forming , ironwork and steel blazing in the sun amid a sea of color , uniforms of green and red and blue in their thousands , in their tens of thousands , all the massed regiments filing into their battle-lines like a monstrous ballet , to the accompaniment of the shrill animal cries of horses , the jar and clatter of the wheels of the supply-carts , the thundercloud-rumble of the field guns .