What factors led to the military success of Ancient Sparta?

I am wondering what the main reasons are that the spartans were so successful on a military level. Any society based examples would help too, but any factor would be appreciated.What factors led to the military success of Ancient Sparta?Unlike the other city states, Sparta's was a pure military state, each man trained from the age of 7yrs to become a professional killer. Sparta's success lay in this extensive training, in particular in the formation of the phalanx, as each man's shield protected the left hand side of his neighbor. As this formation contained men who had spent their lives training, messing, sleeping and being educated together this established a very tight bond, not often broken. Also the state promoted mentoring, each boy during training and education was sponsored by an elder who guided him, ( in sex as well). Thus the phalanx consisted of a body of men who not only knew the person to his left but everyone forming it and trusted that no man would let his brother down.What factors led to the military success of Ancient Sparta?I would think it was their training. Also, their soldiers were encouraged to sleep with each-other, this is confusing at first, but when you are fighting to keep yourself alive you fight hard, when you are fighting so that you AND your lover survive, you fight hardest (no pun intended)What factors led to the military success of Ancient Sparta?They were the best at the phalanx, which was the prominent military strategy at the time in that area. Their prowess was fairly short lived, because tools of warfare like the bow and arrow came into large use, and due to the new mobility the phalanx was fairly useless.