Complex sentence: Although "Artesh" also means army as well, Sepāh has a connotation that is more security driven as opposed to Artesh, which is more militaristic, and henceforth, is used to refer to the general Armed Forces.
Split into simpler sentences: Although "Artesh" means army as well, Sepāh has a connotation of security. By contrast Artesh has a more militaristic meaning and is therefore used to refer to the general Armed Forces.