Indonesia is consist of many kingdoms that united in 17th August 1945 thus becomes Indonesian Independent Day. Each kingdoms has their own culture, language , etnic and race so they have unity language for formal business like in government, school, etc that root from Malay language : bahasa Indonesia . This language already used for trading language from long time ago around Indonesia and South East Asia and has independent using such Java language has many type : there is language for monarchy class , for common class , for market class ,  so it is not independent language , can not be use for uniting diversity .  Most  of culture , language and race  had get influenced according to  the trader or  colonial who occupied the land  like  in Sumatera got influenced by the trader from many countries in Europe so many language close to English . 

People in Sumatera most is the Proto Malays ( Caucasoid Malays ) descendant and Batak people is one of the etnic group of them from the first world migration due to ice age ended then the second migration brought Noro Malays ( type of Mongoloid ) that spread all over Indonesia like in Java, Kalimantan and Celebes .People in Celebes had mixed with Portugues by inter racial marriage during colonialism but their traditional house , some words and sarchopagi like Kalamba and waruga same with Batak people in Sumatera  . People in Java has the similar culture and instrument music with Thailand and Burma but  also had has strong influenced by India in Hindu age that can be seen from their name using India name . Most of their culture are closed to India culture like Ramayana story . People in Maluku ( Moluccas ) considered as people from Cartagena or Africa mixed with Mongoloid and some with Portuguess make them real unique race but then people found that they have tradition and language that almost same with people in Hawaii . During under occupied by the Portugues then occured inter racial marriage. People in Papua is fom Africa.

There are very few records about the early history in Indonesia and not enough have been researched about the subject. Only the history of the coastal areas is partly known. The inland were unknown and there were not much exchange of contacts except for trade. Records of the time were made on palm leaves and other perishable material. In year 100 Indian scholars reported about a kingdom in Sumatra and Java called "Dvipantara" or "Jaya Dwipa". China sent envoys to Sumatera and Arabs and Persians traded in Sumatra. The Egyptian pharaohs bought camphor from Barus on the west coast near Sibolga . Even the Greeks mention Sumatera.

Around the 2nd century AD Indian traders brought in Hinduism to Sumatra but only in parts of Sumatra for example the Hindu temple in Padangsidimpuan ; Candi Portibi. In the 6th to the 13th century the Malay trading nation Sriwijaya in South Sumatra controlled Malacca Straits , India, China, and Indonesia and built Borobudur Temple  around century 7th in Java but then Java allied with India to attck and ruin Sriwijaya nation in around end of century 14th . Around century 14th Portuques came to Sumatera for trading  spices , coffee, tea, tobacco, rubber, cocoa , etc such very rich and fertile land, that is why difficult for you to find history record of Sumatera, all the traders who had lived in Sumatera  hide its just for their own purpose in order to avoid competitors then the English play the role marked by many old companies of English already established in Sumatera from long time ago : look small but exist till now sounds like not fame in the world but have taken strong root in Indonesia market even some to aboard.

Both Marco Polo and Ibn Battuta visited Pasai and North Sumatra in the 12th-13th century. In these period there was a kingdom called Aru in the area of present Medan. The first Muslim ruler in Indonesia was Sultan Malikul Saleh in Pasai, Aceh in the end of the 13th century. In 1350 the North Javanese Majapahit kingdom conquered the Pasai and Aru kingdoms. In the end of the 14th century Majapahit started to lose its power.

The Arabs expanded their trade considerably with Indonesia in the 14th century and Islam spread along the coasts of Sumatra. Islam also became an important concept for coastal areas in countering the threat of Portuguese and Dutch colonialism.

The Acehnese were traders and expanded their sphere of interest south and eastward. Aceh became an important trading power, but also a religious and educational center.

In 1602 the Dutch East India Company (VOC) was founded and granted monopoly east of South Africa with a right to make war and peace. In 1694 the VOC had its first contacts with the Batak people around Lake Toba.

When France occupied Holland during the Napoleon war the British East India Company temporarily took over from VOC in Indonesia (1811-1816). Under this period Sir Stamford Raffles introduced partial self-government, abolished the slave trade, and introduced a modern land-tenure system. In 16th century Dutch brought slaves from Java to work in plantation in some area in Sumatera to reduce over population and jobless in Java .He even was the first European to dig the Borobudur temple in 1811  from the earth 200m covered by eruption of mount merapi in  central Java. During his reign he lived in Bencoloen , Sumatera as botanist he explored almost all jungle in Sumatera to collect many plants and animal named its accordingly then send archive devote to the Queen .

The Dutch, when they came back to Java, intensified their colonial rule. But this sparked widespread revolts for freedom. The revolts were however suppressed one after the other. The London agreement between the Dutch and the English of 1824 had given the Dutch more free room in Sumatera and Jawa and made them more aggressive but not all the kingdom can be occupied because kingdoms in Sumatera was already influenced by the trader from European in strategy and skill more over they were brave to fight.

In the 1820's Aceh began again to emerge as a commercial and political power. Aceh became the biggest black pepper exporter in the world. In 1858 the Dutch took Siak in North Sumatra through a treaty in order to prevent British interests from succeeding. They claimed the oil rich Langkat and Deli, infringing on Acehnese territory. Between 1870 and 1910 the Dutch tried to take complete control over all areas they claimed. This era was the height of their imperialism. Indonesia  or "The Netherlands Indies" was vital to the Dutch industrialization. In 1904 a Dutch military expedition takes control over the Batak region.

In 1861 European missionaries start spreading Christianity around Lake Toba. Tobacco cultivation is introduced in the Medan area in 1865. In 1871 the English and the Dutch sign the Treaty of Sumatra and The Dutch gets a free hand. In 1873 they declared war on Aceh. The Batak war begins in the same year and lasts until 1894 then King Sisingamangaraja XII united all local Batak leaders and led the Bataks in the field till died in 1902 , his general came from Aceh . The war in Aceh became very expensive for the Dutch. Aceh was the richest, best armed and best organized opponent to ever face colonial expansionism. Aceh fell officially into Dutch hands in 1913 after heavy losses on both sides . So , these two places were hard to defeated by the colonial .

In 1906 rubber plantations with new varieties start to develop fast. The plant was brought in from South America to Java in 1876. In 1922 the new harbor Belawan starts to serve northern Sumatra. In February 1942 a revolt starts against the Dutch in North Sumatra and Aceh, with Japanese support. On March 1 the Japanese make an air raid on Medan. On March 28 the last Dutch force in Sumatra surrenders to the Japanese in Kutacane, Aceh. After World War II British troops land in Indonesia as a contingent of the Allied Forces to disarm the Japanese. Dutch troops came along with the British with the ultimate aim of regaining control of Indonesia. They landed in North Sumatra on June 10, 1945.

On August 17, 1945, Soekarno (1901-1970) reads a unilateral Declaration of Independence. This date is now the Indonesian National Day. On November 10, 1945, fighting broke out between British troops and the newly formed Indonesian Republic Army. The British turned to an all-out combat from the sea, air and land. The Indonesian forces had to withdraw from urban battles. Instead they formed guerrilla units. The Dutch sent in more troops to attack Indonesian strongholds. In February 1949 the Dutch were threatened by the Americans to be excluded from the Marshall plan, because of  its war in Indonesia. A Round Table conference started in The Hague on August 23, 1949, under the auspices of the UN. On November 2 Holland recognized the sovereignty of the Republic of Indonesia. On December 27, 1949 the Dutch East Indies ceased to exist. On December 1949 the Dutch formally transferred sovereignty to Indonesia.

It is a popular belief that the Dutch ruled Indonesia for 350 years it was only in Java because actually no Indonesia before century 19th and Indonesia is many kingdoms that united and each kingdom was not at the same time being occupied  by the Dutch because they could defend their territority  , some places to East like Moluccas ( Maluku and Celebes ) were under occupied by Portuguess since century 15th some places in Sumatera just under occupied  late in centruty 19th like Aceh region and Batak land because some area was dwelling by many trades from different nations. However, most areas of present day Indonesia came under Dutch control in the second half of the 19th and the first half of the 20th century. The Dutch built only limited infrastructures and were not very interested in educating the Indonesians. Their two major and lasting Dutch accomplishments in Indonesia were the introduction of a national language, Indonesian, and the formation of one nation, Indonesia. Considering how much they took, it is amazing how little they gave that was why they lost in war not became the winner like the British.

Before independence all of Sumatra was called "Gouverment Van Sumatra" headed by a governor sitting in Medan. In 1950 Sumatra was organized in three provinces where Aceh became incorporated under Medan. This led to a rebellion in Aceh in 1953. In 1957 Aceh became its own province, as once was promised before they joined the Republic.

In February 1958 a rebellion started in Bukit Tinggi, West Sumatra. It called itself Pemerintah Revolusioner Republik Indonesia (PRRI). They were joined by rebellions in Sulawesi and got training, weapons, and active involvement from CIA. They did however not get sufficient local support in North Sumatra and in Aceh. The foreign oil companies continued to pay their taxes to Jakarta. Later in 1958 the Indonesian army landed in Medan. They secured the oil fields and prevented a planned American intervention. The rebels were driven out of Medan on March 17 and a month later Padang and Bukit Tinggi were cleared. Only some guerilla fighting in remote areas continued. The American involvement badly hurt its relations with Indonesia and made the Indonesian communist party more popular. The Indonesian communist party became the biggest outside the communist world.

In 1965, after a failed communist coup attempt, Soeharto starts to squeeze out Sukarno ( the first president ) and in 1967 he became the second president. Soeharto stabilized Indonesian politics with harsh methods and made the economy start growing. However, democracy was set aside, the economy came under domination by huge monopolies, and the corruption developed into extreme proportions. Civil law was paralyzed. From his reign issue of conflict between religion was heard . In Aceh a rebellion was crushed and a martial law in the eastern and northern parts of Aceh was in force for 10 years until 1998. Soeharto politics finally lead to a total economic collapse in the beginning of 1998. Medan, like Jakarta and other major towns, was hit by riots that forced the president to step down.

In May 1998 the vice president of Soeharto, B.J. Habibie becomes president. In 1999 Abdurrahman Wahid (Gus Dur) became the new President with Soekarno's daughter Megawati Sukarnoputri as Vice President, appointed by a democratically elected parliament.
In Aceh martial law war once more broke out ian martial law was introduced once again in 2002. Not until after the Tsunami in the end of 2004, a peace accord could be worked out and finally signed in Helsinki. App. 120.000-150.000 people were killed by the tsunami in Aceh.

In 2004, in the first direct presidential elections ever, Megawati Soekarno Poetri . She lost power to the present President, Susilo Bambang Yudhoyono who also won the following election in 2009. Elections are held every fifth year and the next one is scheduled to 2014.