통신사는 조선이 일본에 파견한 사절단으로 관료와 학자, 문인 등 그 규모가 300~500명에 달했으며, 왕복에 1년이나 걸렸다. 조선은 1404년(태종4)부터 1811년(순조11)까지 총65회 사절단(이중 통신사의 명칭으로 파견된 것은 총 20회)을 파견하였다.

통신사의 대표적인 사례로는 1590년 황윤길黃允吉이 도요토미 히데요시 豊臣秀吉를 만난 것을 들 수 있다. 통신사의 임무를 마치고 귀국한 서인 출신의 황윤길은 장차 일본이 반드시 침략해 올 것이므로 이를 대비하야 한다고 주장하였다. 이때 부사副使로 동행했던 동인 출신의 김성일金誠一의 보고 내용과 다르다는 이유로 그의 의견을 묵살하였다. 1592년 임진왜란이 일어나자 선조는 그의 말을 좇지 않았음을 후회하였다고 전한다.

일본에 파견한 사절단 중 선조 40년인 1607년과 1617년, 1624년에 파견한 것은 회답겸쇄환사回答兼刷還使라 하였다. 이것은 일본이 보내온 국서에 대한 회답回答과 임진왜란 때 납치되어 간 사람들을 데려오는 쇄환刷還에 목적이 있었기 때문이다. 3차에 걸친 회답겸쇄환사를 통해 약 7,600여명이 조선으로 돌아왔다.

1607
Joseon│Restoration of Diplomatic Relations with Japan & Resumption of Envoy Dispatch
Tonghsinsa was a delegation dispatched to Japan, and its size was up to 300~500 people including government officials, scholars and literary persons, etc., and it took them as many as 1 year to go to Japan and back. Joseon dispatched the delegation a total of 65 times(among this, dispatch in the name of Tongshinsa was done 20 times in total) from 1404(during the 4th ruling year of King Taejong) until 1811 (during the 11th ruling year of King Sunjo).

The representative case of Tongshinsa(Joseon envoy) was that Hwang Yun-kil met with Toyotomi Hideyoshi in 1590. Hwang Yun-kil from the Seoin clique who returned home after finishing his duties as Tongshinsa(Joseon envoy) argued that Japan would definitely attack Joseon, and Joseon should make a thorough preparation for it. At that moment, his opinion was dismissed for the reason that Hwang's view was different from the report by Kim Seong-il from the Namin clique who accompanied Hwang as an assistant envoy. Historical records have it that when the Japanese invasion of Korea broke out in 1592, King Seonjo greatly regretted not following Hwang's advice.
The dispatch of Joseon envoys to Japan in 1607(during the 40th ruling year), in 1617 and 1624 among the delegations dispatched to Japan was called an envoy for reply and repatriation. It's because the dispatch was aimed at getting the Japanese reply to Joseon's sovereign messages and repatriating the people, who were abducted during the Japanese Invasion of Korea in 1592, to Joseon.
Through the three-time dispatch of the Joseon envoys for reply and repatriation, about 7,600 people finally returned home.