Otto II's coronation allowed marriage negotiations to begin with the East. Only in 972, six years later, under the new Byzantine Emperor John I Tzimiskes, was a marriage and peace agreement concluded, however. Though Otto I preferred Byzantine Princess Anna Porphyrogenita, daughter of former Byzantine Emperor Romanos II, as she was born in the purple, her age (then only five years old) prevented serious consideration by the East. The choice of Emperor John I Tzimisces was his niece Theophanu, who was the soldier-emperor's niece by marriage. On April 14, 972, the sixteen-year-old Otto II was married to the fourteen-year-old Eastern princess, and Theophanu was crowned empress by the Pope.