With limited resources Muawiyah went about creating allies. Muawiyah married Maysum the daughter of the chief of the Kalb tribe, that was a large Jacobite Christian Arab tribe in Syria. His marriage to Maysum was politically motivated. The Kalb tribe had remained largely neutral when the Muslims first went into Syria. After the plague that killed much of the Muslim Army in Syria, by marrying Maysum, Muawiyah started to use the Jacobite Christians, against the Romans. Muawiya's wife Maysum (Yazid's mother) was also a Jacobite Christian. With limited resources and the Byzantine just over the border, Muawiyah worked in cooperation with the local Christian population. To stop Byzantine harassment from the sea during the Arab-Byzantine Wars, in 649 Muawiyah set up a navy; manned by Monophysitise Christians, Copts and Jacobite Syrian Christians sailors and Muslim troops.