The naval history of Japan began with early interactions with states on the Asian continent in the 3rd century BCE during the Yayoi period. It reached a pre-modern peak of activity during the 16th century, a time of cultural exchange with European powers and extensive trade with the Asian continent. After over two centuries of self-imposed seclusion under the Tokugawa shogunate, Japan's naval technologies became outdated compared to Western navies. The country was forced to abandon its maritime restrictions by American intervention with the Perry Expedition in 1854. This and other events led to the Meiji Restoration, a period of frantic modernization and industrialization accompanied by the re-ascendance of the Emperor's rule and colonialism with the Empire of Japan. Japan became the first industrialized Asian country in 1868, by 1920 the Imperial Japanese Navy was the third largest navy in the world and arguably the most modern at the brink of World War II.
The Imperial Japanese Navy had a history of successes, sometimes against much more powerful foes as in the 1894–1895 Sino-Japanese War, the 1904–1905 Russo-Japanese War, and early naval battles during World War II. In 1945, towards the end of the conflict, the navy was almost completely destroyed by the United States Navy. Japan's current navy is a branch of the Japan Self-Defense Forces (JSDF) called the Japan Maritime Self-Defense Force (JMSDF). In 2015, the JMSDF was ranked by Credit Suisse as the fourth most powerful military in the world. However, it is still denied any offensive role by the nation's post-war Constitution and public opinion.
Prehistory
Japan was connected to the Asian continent via land during the glacial maximum of the last ice age around 20,000 BCE. This allowed for the transmission of flora and fauna, including the establishment of the Jōmon culture. The land bridges disappeared in the Jōmon period around 10,000 BCE. After that period however, Japan became an isolated island territory, depending entirely on sporadic naval activity for its interactions with the continent. The shortest seapath to the continent (besides the inhospitable northern path from Hokkaidō to Sakhalin) then involved two stretches of open water about 50 kilometers wide, between the Korean peninsula and the island of Tsushima, and then from Tsushima to the major island of Kyūshū.
Early historical period
Ambassadorial visits to Japan by the later Northern Chinese dynasties Wei and Jin (Encounters of the Eastern Barbarians, Wei Chronicles) recorded that some Japanese people claimed to be descendants of Taibo of Wu, refugees after the fall of the Wu state in the 5th century BCE. History books do have records of Wu Taibo sending 4000 males and 4000 females to Japan.
Yayoi Period
The first major naval contacts occurred in the Yayoi period in the 3rd century BCE, when rice-farming and metallurgy were introduced, from the continent.
The 14 AD incursion of Silla (新羅, Shiragi in Japanese), one of the Three Kingdoms of Korea, is the earliest Japanese military action recorded in Samguk Sagi. According to that record, Wa (the proto-Japanese nation) sent one hundred ships and led an incursion on the coastal area of Silla before being driven off.
Yamato Period
During the Yamato period, Japan had intense naval interaction with the Asian continent, largely centered around diplomacy and trade with China, the Korean kingdoms, and other continental states, since at latest the beginning of the Kofun period in the 3rd century. According to a mythological account in the Kojiki and Nihon Shoki, Empress Jingū is claimed to have invaded Korea in the 3rd century, and to have returned victorious after three years. Whether a Japanese political entity actually ruled a part of Korea in ancient times is debated, but considered unlikely for that time period.
Other than the expedition of Empress Jingū, battle of Hakusukinoe (白村江), one of the earliest historical events in Japan's naval history took place in 663. Japan sent 32,000 troops and possibly as many as 1,000 ships to Korea to support the declining Baekje kingdom (百済国; contemporary records suggest that Baekje and Yamato Japan were allies, and that their royal/imperial families were possibly related) against Silla and Tang-dynasty China. They were defeated by the T'ang-Silla combined force.
The Azumi people were a warrior tribe from northern Kyushu. They were extremely skilled seafarers. The Azumi gained early contact with the Yamato Court and provided maritime trade links and influenced the Yamato Court's military and diplomatic approach in the seas. Thus the Japanese imperial government employed them as their naval force from the 3rd to 5th centuries.