So low had Sparta sunk, that she was fain to send envoys to beg the assistance of the Athenians. This request was acceded to; and shortly afterwards an alliance was formed between the two states, in which Sparta waived all her claims to superiority and headship. During the next two years the Thebans continued steadily to increase their power and influence in Greece, though no great battle was fought. In B.C. 368 Pelopidas conducted a Theban force into Thessaly and Macedonia. In Thessaly he compelled Alexander, who, by the murder of his two brothers, had become despot of Pherae and Tagus of Thessaly, to relinquish his designs against the independence of Larissa and other Thessalian cities, and to solicit peace. In Macedonia he formed an alliance with the regent Ptolemy: and amongst the hostages given for the observance of this treaty was the youthful Philip, son of Amyntas, afterwards the celebrated king of Macedon, who remained for some years at Thebes. In the following year Pelopidas and Ismenias proceeded on an embassy to Persia. Ever since the peace of Antalcidas the Great King had become the recognised mediator between the states of Greece; and his fiat seemed indispensable to stamp the claims of that city which pretended to the headship. The recent achievements of Thebes might entitle her to aspire to that position: and at all events the alterations which she had produced in the internal state, of Greece, by the establishment of Megalopolis and Messene, seemed to require for their stability the sanction of a Persian rescript. This was obtained without difficulty, as Thebes was now the strongest state in Greece; and it was evidently easier to exercise Persian ascendency there by her means, than through a weaker power. The Persian rescript pronounced the independence of Messene and Amphipolis; the Athenians were directed to lay up their ships of war in ordinary; and Thebes was declared the head of Greece.