Now, his influence extended over much of Bulgaria, Greek and Turkish Thrace and also parts of southeastern Romania: from the Strymon and Iskar rivers in the west to the Black Sea and the Propontis in the east as well as the Haemus and the mouth of the Danube (which was ruled by the tributary Getae) in the north. According to Thucydides, the Odrysian state was "very powerful, and in revenue and general prosperity exceeded all the nations of Europe which lie between the Ionian Sea and the Euxine [Black Sea]." In the south, much of coastal Thrace had passed under the rule of Athens, making them direct neighbours of the Odrysians. The Athenians had already taken some interest in the Thracian interior before 431, but it was in said year when they concluded an alliance with Sitalces against Perdiccas II of Macedon in the west. This pact was cemented by a dynastic marriage, as Sitalces would marry the sister of the Athenian ambassador, Nymphodoros of Abdera. Sitalces' son Sadokos was sent to Athens and was granted the Athenian citizenship. Sitalces, apparently an experienced leader with political acumen, would prove his commitment to the alliance in the next year, when he arrested a Peloponnesian embassy that tried to persuade him to join the Spartan side and handed it over to Athens. At the turn of the year 428, Sitalces raised a massive, multi-ethnic army to march against Macedon and insurgents on the Chalkidiki peninsula. His army consisted of a variety of Thracians (some, like those of the Rhodopes, were independent, but joined nonetheless), Getae and some Paeonians. While Sitalces managed to subjugate some of the Thracian tribes of the lower Strymon, his invasion of eastern Macedon and the Chalkidiki was less successful, as his opponents avoided open combat and simply hid behind their walls. The Odrysian army had not the means to storm them, plus winter was approaching and food supplies were running out. Furthermore, the Athenian force that was promised to them never arrived, perhaps because Athens feared the might of the unleashed Thracian kingdom. After failed negotiations with Perdiccas II, Sitalces retreated back home. Thus, after only 30 days the Odrysian invasion had come to an end. Seuthes I Sitalces was succeeded in 424 by his nephew Seuthes I after the former was killed while campaigning against the Triballi, who resided north of the western Haemus. Throughout his reign,