After a protracted siege, he took Rhegium in 386 and sold the inhabitants as slaves. He also pillaged the temple of Caere (then allied with Rome) on the Etruscan coast. In the Adriatic, to facilitate trade, Dionysius founded Ancona, Adria and Issa. After him, the Adriatic became a sea of Syracuse. In the Corinthian War, he joined the side of the Spartans and assisted them with mercenaries and ships (which contributed in blocking the Athenians' supplies from the Black Sea forcing them to peace) .