The national flag of Japan is a rectangular white banner with a red circle at its center. The flag is officially called the Nisshōki (日章旗, 'flag of the sun'), but is more commonly known in Japan as the Hinomaru (日の丸, 'ball of the sun'). It embodies the country's sobriquet: the Land of the Rising Sun.
The Nisshōki flag is designated as the national flag in the Act on National Flag and Anthem, which was promulgated and became effective on 13 August 1999. Although no earlier legislation had specified a national flag, the sun disc flag had already become the de facto national flag of Japan. Two proclamations issued in 1870 by the Daijō-kan, the governmental body of the early Meiji period, each had a provision for a design of the national flag. A sun disc flag was adopted as the national flag for merchant ships under Proclamation No. 57 of Meiji 3 (issued on 27 February 1870), and as the national flag used by the Navy under Proclamation No. 651 of Meiji 3 (issued on 3 October 1870). Use of the Hinomaru was severely restricted during the early years of the Allied occupation of Japan after World War II; these restrictions were later relaxed.
The sun plays an important role in Japanese mythology and religion, as the Emperor is said to be the direct descendant of the Shinto sun goddess Amaterasu, and the legitimacy of the ruling house rested on this divine appointment. The name of the country as well as the design of the flag reflect this central importance of the sun. The ancient history Shoku Nihongi says that Emperor Monmu used a flag representing the sun in his court in 701, the first recorded use of a sun-motif flag in Japan. The oldest existing flag is preserved in Unpō-ji temple, Kōshū, Yamanashi, which is older than the 16th century, and an ancient legend says that the flag was given to the temple by Emperor Go-Reizei in the 11th century. During the Meiji Restoration, the sun disc and the Rising Sun Ensign of the Imperial Japanese Navy and Army became major symbols in the emerging Empire of Japan. Propaganda posters, textbooks, and films depicted the flag as a source of pride and patriotism. In Japanese homes, citizens were required to display the flag during national holidays, celebrations and other occasions as decreed by the government. Different tokens of devotion to Japan and its Emperor featuring the Hinomaru motif became popular among the public during the Second Sino-Japanese War and other conflicts. These tokens ranged from slogans written on the flag to clothing items and dishes that resembled the flag.
Public perception of the national flag varies. Historically, both Western and Japanese sources have described the flag as a powerful and enduring symbol to the Japanese. Since the end of World War II (the Pacific War), the use of the flag and the national anthem Kimigayo has been a contentious issue for Japan's public schools, and disputes about their use have led to protests and lawsuits. Several military banners of Japan are based on the Hinomaru, including the sunrayed naval ensign. The Hinomaru also serves as a template for other Japanese flags in public and private use. The desecration of the Hinomaru is illegal.
The exact origin of the Hinomaru is unknown, but the rising sun has carried symbolic meaning since the early 7th century. Japan is often referred to as "the land of the rising sun". The Japanese archipelago is east of the Asian mainland, and is thus where the sun "rises". In 607, an official correspondence that began with "from the Emperor of the rising sun" was sent to the Chinese Emperor Yang of Sui.
The sun is closely related to the Imperial family, as legend states the imperial throne was descended from the sun goddess Amaterasu. The religion, which is categorized as the ancient Ko-Shintō religion of the Japanese people, includes nature worship and animism, and the faith has been worshiping the sun, especially in agriculture and fishing. The Imperial God, Amaterasu-ōmikami, is the sun goddess. From the Yayoi period (300 BCE) to the Kofun period (250 CE) (Yamato period), the Naikō Kamonkyō, a large bronze mirror with patterns like a flower-petal, was used as a celebration of the shape of the shining sun and there is a theory that one of the Three Sacred Treasures, Yata no Kagami, is used like this mirror.
During the Eastern expedition, Emperor Jimmu's brother Itsuse no Mikoto was killed in a battle against the local chieftain Nagasunehiko ("the long-legged man") in Naniwa (modern-day Osaka). Emperor Jimmu realized, as a descendant of the sun, that he did not want to fight towards the sun (to the east), but to fight from the sun (to the west). The Emperor's clan therefore went to the east side of Kii Peninsula to battle westward. They reached Kumano (or Ise) and went towards Yamato. They were victorious at the second battle with Nagasunehiko and conquered the Kinki region.
The use of the sun-shaped flag was thought to have taken place since the emperor's direct imperial rule (親政) was established after the Isshi Incident in 645 (first year of the Taika).
The Japanese history text Shoku Nihongi, completed in 797, has the first recorded use of the sun-motif flag by Emperor Monmu's Chōga (朝賀, 'new year's greetings ceremony') in 701 (the first year of the Taihō era). For the decoration of the ceremony hall on New Year's Day the Nissho (日像, 'the flag with the golden sun') was raised.
One prominent theory is influenced by the results of the Genpei War (1180–1185). Until the Heian period, the Nishiki flag (錦の御旗, Nishiki no mihata), a symbol of the Imperial Court, had a golden sun circle and a silver moon circle on a red background. At the end of the Heian era, the Taira clan called themselves a government army and used the red flag with a gold circle (赤地金丸) as per the Imperial Court. The Genji (Minamoto clan) were in opposition so they used a white flag with a red circle (白地赤丸) when they fought the Genpei War (1180–1185). When the Taira clan was defeated, the samurai government (幕府, bakufu) was formed by the Genji. The warlords who came after such as Oda Nobunaga and Tokugawa Ieyasu realized they were successors of Genji, and so raised the Hinomaru flag in battle.
In the 12th-century work The Tale of the Heike, it was written that different samurai carried drawings of the sun on their fans. One legend related to the national flag is attributed to the Buddhist priest Nichiren. Supposedly, during a 13th-century Mongolian invasion of Japan, Nichiren gave a sun banner to the shōgun to carry into battle.
During the Battle of Nagashino (28 June 1575), Oda Nobunaga and Tokugawa Ieyasu's allied forces fought Takeda Katsuyori. Both Nobunaga and Ieyasu had their own flags with family crests, but they also held the Hinomaru. On the other hand, the Takeda clan side also raised the Hinomaru. Therefore, the Hinomaru was used as a national symbol.
One of Japan's oldest flags is housed at the Unpo-ji temple in Kōshū city, Yamanashi Prefecture. Legend states it was given by Emperor Go-Reizei to Minamoto no Yoshimitsu and has been treated as a family treasure by the Takeda clan for the past 1,000 years, and is at least older than 16th century.
In the 16th century unification period, each daimyō had flags that were used primarily in battle. Most of the flags were long banners usually charged with the mon (family crest) of the daimyō lord. Members of the same family would have had different flags to carry into battle. The flags served as identification and were displayed by soldiers on their backs and horses. Generals also had their own flags, most of which differed from soldiers' flags due to their square shape.
In 1854, during the Tokugawa shogunate, Japanese ships were ordered to hoist the Hinomaru to distinguish themselves from foreign ships. Before then, different types of Hinomaru flags were used on vessels that were trading with the U.S. and Russia. The Hinomaru was decreed the merchant flag of Japan in 1870 and was the legal national flag from 1870 to 1885, making it the first national flag Japan adopted.