Spartiate numbers continued to decline in the second and third decades of the fourth century (for their numbers in the 390s, see Box 15.2). No matter how much the Lacedaemonians strove to use non-Spartiate troops whenever possible and no matter how successfully they used diplomatic means to achieve their aims without fighting, Spartiate numbers did not recover. Because it took twenty-three years in the agoge and thereafter admittance to a syssition (see Box 13.3) to make a Spartiate, whenever a Spartiate died young, there was no immediate replacement.
A Spartiate, as a professional soldier, had no trade: his sole income was half of what the Helots on his land produced (Plut. Lyc. 24). Out of this income the Spartiate paid his membership dues to his syssition (Plut. Lyc. 12), and if he could not pay them, then he lost his membership, dropped out of the ranks of the Spartiates, and became a so-called hypomeion, an "inferior" (for the term, see Xen. Hell. III 3,6) Here the absence of primogeniture comes into play. If a Spartiate had, say, four sons, then each son inherited a quarter of his land. If a quarter were not large enough for sustaining a family and paying the dues to a syssition, then all four sons dropped out of the Spartiate class. In other words, even if a given Spartiate did have a large number of sons, they would not necessarily have been replacing a Spartiate who had died without producing a son.
Moreover, even if in theory all Spartiates held equal plots of land and in theory each Spartiate male at birth was assigned to one such plot (Plut. Lyc. 16), in reality the land was very unevenly distributed, and sons inherited their father's land (thus, plainly, Arist. Pol. 1270b). The lack of primogeniture worked unevenly over time to produce such a distribution. Additionally, although it was illegal to sell land in Sparta, there were ways to circumvent the law such that a few families eventually acquired large landholdings even as most were restricted to the smallest of plots (Arist. Pol. 1270a). For example, if a poor Spartiate could not pay his dues to his syssition in bad years, he might "borrow" from a wealthy landholder - to whom he might then "give" a bit of land. Technically, he had not "sold" any land; and while he may have secured his status as a Spartiate for his lifetime, he had probably ruined any chance which his son might otherwise have had. The "giving" of land in this way worked to produce an uneven distribution also. Aristotle (l. c.) impatiently notes that the Lacedaemonians ought to have made the very transfer of land illegal - not merely the selling of it.
Aristotle also comments that if the Lacedaemonians' land had been evenly distributed so as to maximize the number of Spartiates, it could have supported 30,000 infantrymen and 1,500 cavalrymen to boot. As it was, Aristotle continues, after the Battle of Leuctra in 371 (in which Spartiate casualties were high), the number of Spartiates dropped to below a thousand.
This peace, the third renewal of the original one (Diod. XV 76; cf. Isoc. VI 27, confirming Persian involvement; Xen. Hell. VII 1,36-37, records the initial terms proposed by the Boeotians; VII 4,6-11, speaks of the Peace itself). For the first time, duly authorized representatives of the Boeotian League swore the Peace - that is to say, the Boeotian League won full diplomatic recognition. Also swearing the Peace were the Messenians, whose new independence was thus recognized (Diod. XV 81 and 90). The Lacedaemonians remained aloof as they could not bear to swallow this bitter pill. Their allies, however, they permitted to make the peace (Xen. Hell. VII 4,9 ): Corinth, Phleius, and Epidaurus are known to have done so (Isoc. VI 91). Of the Lacedaemonians’ enemies, Argos (Xen. Hell. 4,11) and Athens also (Dem. XIX 137; cf. Xen. Hell. VII 4,1) swore this Peace. Others surely did as well. It was a spectacular achievement for the Boeotians and their chief diplomat, Pelopidas.
The Boeotians now built a fleet of a hundred triremes and challenged the second Athenian League on the sea (Diod. XV 79; Isoc. V 53; Dem. XIV 22; Plut. Phil. 14). Diodorus reveals little of this fleet’s activities though it was apparently active in the Propontis near Byzantium (Isoc. l. c.). The Athenians under Timotheus, allegedly in 364, relieved a siege of Cyzicus in the Propontis (Diod. XV 81) - it may have been the Boeotians besieging Cyzicus, but Diodorus does not say. Despite the Boeotians’ ambitions, little came of their attempt at naval power; and the expenses of a fleet may well have exceeded their long-term financial capacity.
In 364 the Boeotian League destroyed one of the cities in the League itself, Orchomenus. Orchomenus had been brought into the League much against its will in the late 370s and prominent Orchomenians had allegedly been plotting against the League in 364. The Boeotians responded by razing Orchomenus to the ground, slaying the men, and selling the women and children into slavery (Diod. XV 79). The other Greeks never forgot the act; when Alexander the Great had Thebes itself razed in 335, he took good care to present his act as just retribution, decreed by other Greeks, for what had happened to Orchomenus in 364 and Plataea in 373 (Arrian, Anab. I 9).
Meanwhile the Boeotian ascendancy had made firm allies of two erstwhile foes, Athens and Sparta. Thebes had actually been one of the first members of the Second Athenian League (Harding, Nr. 35), but regardless of whether or not it ever officially withdrew, its membership had effectively ended by 373 at the latest with the destruction of Plataea. Already in the aftermath of Leuctra (in 371), Athens and Sparta had made an alliance (Xen. Hell. VI 5,1-2). The Athenians sent troops to the Peloponnese in support of the Lacedaemonians in 369 (Xen. Hell. VI 5,49), renewed their alliance with Sparta in 368 (Xen. Hell. VII 1,1-14), and fought against the Boeotians on the Peloponnese in that year (Diod. XV 68-69; Xen. Hell. VII 1,15-21). When the Boeotians invaded Thessaly in 368, the Athenians assisted the Thessalians (Diod. XV 71). Thus, when the Boeotians invaded Arcadia in 362 - intervening in a quarrel within the Arcadian League on behalf of Tegea against Mantinea - the Mantineans and
Those Arcadians allied with them promptly appealed to both Athens and Sparta for aid (Xen. Hell. VII 4,33-5,3; Diod. XV 82). Both responded.
In 362, the Boeotians and their allies fought at Mantinea against the Lacedaemonians, the Athenians, and their allies. The result was in theory a victory for the Boeotians as great as Leuctra (Xen. Hell. VII 5,4-25; Diod. XV 82-87 [Xenophon’s account of the battle is better; for criticism of that in Diodorus, based on Ephorus, see Pol. XII 25f]), but Epaminondas himself fell in the fighting, and the Boeotian troops did not pursue their fleeing opponents after the battle. In the opinion of Ephorus (BNJ 70, Fr. 119; see also Diod. XV 79,2 and Pol., VI 43,6) the Boeotian dominance in Greece had rested on the ability of Epaminondas alone, and with his death it ended.
After the Battle of Mantinea, one last Common Peace came into being. For once Persian involvement is not attested; as the Messenians swore this Peace too, the Lacedaemonians refused to participate (Diod. XV 89).