Kingdom of Thessalonica
The Greeks of Serres in the Kingdom of Thessalonica sent envoys to Boril's commander in Melnik, seeking his assistance against the Latins in early 1209. Henry soon intervened and suppressed their revolt. Boril concluded an alliance with Theodore I Laskaris, Emperor of Nicaea, and Michael I Komnenos Doukas, the Greek ruler of Epirus, against the Latins. He also made peace with Strez who had turned against Nemanjić.