Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.

Let me give you an example: In 1582 the united provinces invited francis, duke of anjou to lead them; but after a failed attempt to take antwerp in 1583, the duke left the netherlands again. after the assassination of william of orange (10 july 1584), both henry iii of france and elizabeth i of england declined the offer of sovereignty. however, the latter agreed to turn the united provinces into a protectorate of england (treaty of nonsuch, 1585), and sent the earl of leicester as governor-general. this was unsuccessful and in 1588 the provinces became a confederacy. the union of utrecht is regarded as the foundation of the republic of the seven united provinces, which was not recognized by the spanish empire until the peace of westphalia in 1648.
The answer to this example can be: In what year did francis, duke of anjou leave the netherlands?
Here is why: The generated question is perfect. Because the question is based on second sentence of the input passage and its answer is 1583.

OK. solve this:
As Tsushima had suffered greatly from its loss of trade with Korea as a result of the invasions, Yoshitoshi of the So family, then dominant in Tsushima, undertook the lead in the peace negotiations by Japan. He sent four peace missions to Joseon in 1599 to normalize relations. The first three were captured and sent directly to Beijing by Chinese troops, but the fourth one, in 1601, successfully obtained from the Joseon court the promise of a normalizing of relations upon the return of remaining Joseon captives. As Ming troops continued to be present in Korea following the withdrawal of Japanese forces, the major incentive for Joseon for the normalization of relations with Japan was the withdrawal of the Chinese soldiers from their territory. The Ming Chinese themselves were causing as much havoc as the Japanese had during the actual conflict, and their presence continued to strain Joseon's national economy and infrastructure. In response to the Joseon request, Yoshitoshi promptly released several Joseon prisoners and between 1603 and 1604 helped the Joseon envoys to repatriate a further 3,000 by organizing negotiations at Kyoto with Tokugawa Ieyasu, by then the Shogun of Japan. In the continuation of the diplomatic talks toward peaceful relations, Joseon in 1606 expanded its conditions and demanded that the Shogun write a formal letter requesting peace, and to extradite the Japanese soldiers who had defiled the Joseon Royal Tombs near Hanseong . Realizing that the Shogunate would never agree to such a request, Yoshitoshi sent a forged letter and a group of criminals instead; the great need to expel the Ming soldiers pushed Joseon into accepting and to send an emissary in 1608. The end result was a return of Joseon prisoners and the restoration of diplomatic and trade relations between the two countries.
Answer:
Who sent four peace missions to Joseon in 1599?