Blood vessels that carry blood away from the heart.
Archery like an artery is away from the heart. Veins flow into the heart. Arteries flow away from the heart.
All archers have to do in a war is fire an arrow, when told. So you put your "thicker" people into your archery section.
Archery section = thicker.
Arteries = thicker.
Note: arteries are thicker than veins.