Why was the Spartan army so consistently successful on the battlefield?

Why was the Spartan army so consistently successful on the battlefield?11-27.-Hodkinson, S. ‘Social Order and the Conflicy of Values’, in M. Whitby (ed.), Sparta. London:Routledge, 2002: 119-124.-Humble, N. ‘Why the Spartans Fight so Well … Even in Disorder? – Xenophon’s View’, in S.Hodkinson and A. Powell (eds), Sparta and War. Swansea: Classical Press of Wales, 2006:219-234.-Millender, E. ‘The Greek Battlefield: Classical Sparta and the Spectacle of Hoplite Warfare’, W.-Riess and G.G. Fagan (eds), The Topography of Violence in the Greco-Roman World. AnnArbor: University of Michigan Press, 2016: 162-194.-Yellin, K. Battlefield Exhortation: The Rhetoric of Combat Leadership. Columbia: University ofSouth Carolina Press, 2008: 23-35.