 Beginning in 1405 , the Yongle Emperor entrusted his favored eunuch commander Zheng He ( 1371 – 1433 ) as the admiral for a gigantic new fleet of ships designated for international tributary missions . The Chinese had sent diplomatic missions over land since the Han dynasty ( 202 BCE – 220 CE ) and engaged in private overseas trade , but these missions were unprecedented in grandeur and scale . To service seven different tributary voyages , the Nanjing shipyards constructed two thousand vessels from 1403 to 1419 , including treasure ships measuring 112 m ( 370 ft ) to 134 m ( 440 ft ) in length and 45 m ( 150 ft ) to 54 m ( 180 ft ) in width . 
