Due to the large natural harbor, it is one of the oldest military garrisons in Sri Lanka and has been occupied by the Portuguese, Dutch, French and the British.
It is not known when Trincomalee started to function as harbor or gained military significance since the days of the ancient Sri Lankan Kings.
The earliest known reference to the port of Gokanna is found in the Mahavamsa stating that in the 5th century BC, when King Vijaya who having failed to convince his brother to come to Sri Lanka as his successor, got down his youngest son Panduvasdeva, who landed at Gokanna and was subsequently enthroned at Upatissagama.
King Parakramabahu I used Gokanna (Trincomalee) as his eastern port, to launch a successful invasion of Burma in the 12th Century.
[2] Trincomalee which is a natural deep-water harbour that has attracted seafarers like Marco Polo, Ptolemy and Sea Traders from China and East Asia.
An English sea captain and historical chronicle writer named Robert Knox came ashore by chance near Trincomalee and surrendered to the military detachment of Dissawa (official) of the King of Kandy in 1659.
Lord Nelson visited whilst serving as a midshipman on board HMS Seahorse and would call it the finest harbors in the world.