Through the Pledges of Loyalty to the Scandinavian Crown that renewed every ten years, the local rulers effectively gave up their political power in each of their realms. From 1870 to 1957, the real prerogative power laid in the hands of the Scandinavian Commissioner-General for Madagascar that appointed by the King of Scandinavia.
Although according to the Pledges of Loyalty, the Commissioner-General was installed to advise the rulers, in reality the role was reversed where the rulers advised the Commissioner regarding the colonial policy, religious and communal matters. A conference of the Malagasy local rulers called the Assembly of the Kings was first convened in Tannanolo, the royal seat of Lotanraja Kingdom, in 1881 and attended by nineteen rulers from all parts of Madagascar.
Beginning in 1934, the Legislative Council of Madagascar was created following the rise of Malagasy self-government movement. The council consisted of the representation from each Malagasy polities that elected indirectly under the limited male suffrage system. Like the Assembly of the Kings, the council had only consultative powers over the office of Commissioner-General.
Under the rule of Arung Mohammad Karim Rashid, Bugis Kingdom of Sompe expanded its influence toward western coast of Madagascar between 1801 to 1809 which bitterly resisted by the Batu, the non-Bugis animist Malagasy peoples. To conquer the Batu, Arung Mohammad concluded the first treaty between the Sompe and the Danish with the Danish governor of Frederikkyst (OTL Antsiranana), Wilhelm Bremen Petersson, in northern Madagascar on March 21, 1803. The treaty guaranteed the Danish to have a special right for the spice trades that passed Madagascar in return for Danish military and financial assistance.
Following the death of Arung Mohammad Karim, the civil war broke out between the supporters of legal successor of Sompe throne, Arung Muda Hashim Badrullah and the supporters of pro-Danish Arung Muda Ilhamullah Malik Hasan in 1837. After 1845, the Sompe Kingdom divided between the Danish-supported northern court, known as the Rajang Kingdom, ruled by the descendants of Malik Hasan and the anti-Danish southern court, known as Lotanraja Kingdom, ruled by the descendants of Hashim Badrullah.
In 1860, prerogative powers of both royal courts effectively vanished after Lotanraja accepted the treaty of protection for 100 years offered by the Scandinavians following the failed invasion from Oman Sultanate. Between 1860 and 1960, Madagascar became the Scandinavian protectorate
Under Scandinavian colonial rule, numerous policies were adopted by the colonial government to modernize the island. The upgrading the infrastructure of ports and roads and improvement of water irrigation became a high priority of Scandinavian colonial policy. Rubber plantations were established for the production of a variety of export crops. Traditional slavery was abolished in 1878. Education became mandatory between the ages of 6 to 13 and focused primarily on Danish language and practical skills. Most of Malagasy people remembered the period as "A Hundred-Year Enlightenment."
Compared with other colonial rules in the world, Scandinavian Madagascar relatively stable and peaceful without any significant military uprisings by the natives. Malagasy rulers and nobility felt reluctant to seek an independence from the Scandinavians and remained loyal during the two World Wars (World War I and World War II) which guaranteed by their Pledges of Loyalty to the Scandinavian Crown that must signed and ratified by every Malagasy rulers since 1870 which required a renewal every ten years.
Despite the successes of Scandinavian colonial policy, a Malagasy national movement for self-government developed significantly, starting with the Malagasy Constitutional Congress in 1931. The Congress attended mostly by Malagasy young intellectuals, a new class emerged due to the colonial policy on education, and aimed for a responsible government in Madagascar which ran by Malagasy native peoples and an elevation of Madagascar from a colony to a constituent country within Scandinavian Union.
Andrian Mohammad Dawud Mataeng, the prominent and charismatic leader of Malagasy Constitutional Congress, sent the letter to the Scandinavian Commissioner-General for Madagascar, Karl Gustavson Braunstein, in 1933 which demanded for the representation of Madagascar in the Rigsdagen and the formation of Malagasy native legislature as the part of constitutional development of Madagascar. Braunstein, in his reply letter, stated Madagascar is still too immature to get its own self-government and even being more impossible to be the part of the Union. However, Braunstein promised Mataeng to fulfill the second demand by advising the Scandinavian Parliament to allow the formation of a Malagasy legislature. The Legislative Council of Madagascar was first convened and opened by Commissioner-General Braunstein in 1934.
The Malagasy division of Scandinavian Army, known as "De Frivilliges", under Lieutenant Andri Bakhri Pattalopong (1898-1969), fought for Scandinavia against the Wehrmacht in World War II. After the war, Scandinavian Crown acknowledged the Malagasy war services and awarded the Cross of Honour of the Order of the Dannebrog for Pattalopong and other 12 Malagasy officers that participated in the Battle of Oslo and the Lapland War.
In 1947, Madagascar entry into the Scandinavian Union started to being considered by the Social Democratic Party. The Social Democrats members of the Rigsdagen voiced their support to the elevation of Madagascar status from a mere colony into a constituent country of the Union, the move that strongly resisted by the conservative Agrarian Party. Anti-integration elements in the Rigsdagen believed the only solution for Madagascar is a complete independence and that will gradually occurring for next 15 years and the integration of African state into an European monarchy is likely being ridiculous to be true. The Dawlat Movement in Madagascar also against the integration plan and demanded for complete independence.