21st of August is the National Maritime Day. It commemorates the 21st of August 1945, when the Indonesian navy got its independence over the Japanese colonial's navy. The Indonesian national navy itself has been existing since the 9th century. It was when the maritime kingdoms (kingdoms located in maritime areas) successfully brought prosperity across the nation, which at that time known as Nusantara.

The greatest maritime kingdom during that time was Sriwijaya Kingdom. Its harbor welcomed a lot of traders from India as a transit venue before continuing their voyage to the east, or vice versa. The history of glorious maritime kingdom also happened during the Majapahit Kingdom, where the navy could unite almost all part of Nusantara under the command of Mpu Nala Admiral. This also happened in Banten, which was an Islamic sultanate. Banten has lots of harbor cities that welcomed traders and visitors from Europe, Middle East, India and China, since the infrastructure there was already state-of-the-art. That harbor city is now known as Jakarta, the current capital city of Indonesia.