Kangjeng Gusti Pangeran Adipati Arya Mangkunegara I, also known as Pangeran Sambernyawa ("Life Reaping Prince"), his birth name was Raden Mas Said (April 7, 1725 – December 28, 1795), established the Puro Mangkunegaran, in Surakarta, Java Island. Thus, he was the first ruler of The Principality of Mangkunegaran.^[1]

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Mangkunegara was given the nickname "Life Reaping Prince" by Nicolaas Hartingh because the prince had brought his enemies to death during the war.^{[citation needed]} Hatingh was the Dutch East India Company's Governor of the Northeast Coast of Java, located in Batavia.

He was born on 7 April 1726 in Kartasura.^[2] Mangkunegara was brought up by his mother, Raden Ayu Wulan and his father, Prince Mangkunegara Kartasura. His maternal grandfather was Prince Sambernyawa Balitar and his paternal grandfather was Amangkurat IV, King of Mataram.

Raden Mas Said (RM Said) war against the Dutch East India Company started with the rebellion in Kartasura Palace on June 30, 1742, which was led by Raden Mas Garendi (a.k.a Sunan Kuning) and destroyed the four meters of Kartasura’s castle wall. Pakubuwono II, the ruler of Kartasura Palace at that time, evacuated himself to Ponorogo Regency. RM Said was 19 years old when he joined his brother, Mangkubumi, to defend the people of Mataram which was oppressed by the Dutch Company, and their king, Pakubuwono II. The two brothers siege the Kartasura Palace, which was called the Dutch puppet Kingdom. When the army sieged the palace, the nobles left the Kartasura Palace to evacuate themselves. RM Said built a fortress in Randuwalang, to the north of Surakarta, and merged his army with Sunan Kuning forces to fight against the Dutch Company. RM Said was promoted and became the warlord. Their army managed to destroy the Surakarta Palace. When Pakubuwono II died, Mangkubumi ran to Semarang to meet the ruler of the Dutch East India Company and asked him so Mangkubumi become the king of Mataram. Of course, the Dutch East India Company did not grant Mangkubumi’s wish. Then, Mangkubumi joins Prince Puger in Sukowati, a district in Surakarta. With the help of the Dutches, all of the Chinese armies drove out from Kartasura Palace, but six months later, Pakubuwono II went back to Kartasura just to find out that his palace had been destroyed.

But the king’s request for reinforcement from the Dutches is not for free, and must be paid expensively; the north region of Java, from Rembang, Pasuruan, Surabaya, and Madura Island must be handed over to the Dutch East India Company. Also, every coronation and promotion in the palace must receive approval from the Dutch Company first. When Prince Mangkubumi declared that he join the army with RM Said, he chose to guerrilla against the Dutch Company in the jungle in Jogjakarta. RM Said married to Ray. Kusumapatahati, the daughter of Kyai Kasan Nuriman. Then, at the age of 22, married again for the second time with Raden Ayu Inten (Kangjeng Ratu Bandara), the daughter of Prince Mangkubumi. When RM Said separated his army from Raden Mas Garendi, and built a headquarters in Panambangan, then declared himself as Price Mangkunegara I. Not long after his declaration, his throne was struck by lightning. This means that RM Said cannot be the king or act like the king in the palace. When the news of the death of Pakubuwono II heard, RM Said met Prince Mangkubumi and asked his parent-in-law to declare himself as a king of Mataram before the coronation of the son of Pakuwubono II. Prince Mangkubumi declared himself as "Sultan Hamengkubuwono", and RM Said was promoted to become the warlord. His wife, Raden Ayu Inten, changed her name to “Kanjeng Ratu Bandara”. But of course, the reign of Mangkubumi wasn’t approved by the Dutch East India Company.

So many events happened after fighting against the Dutch Company, Prince Mangkubumi and Prince Mangkunegara had a conflict about politics. RM Said had to fight the Dutch East India Company alone. And finally, Mataram was divided into two by the Treaty of Giyanti on February 13, 1755. This treaty was rejected by RM Said because it could ruin the unity of the Mataram people. Over the 16 years, RM Said fought 250 marvelous battles against the Dutch Company. From that, the Dutches called RM Said “The Soul Reaper” because he is the nightmare of his enemies. RM Said greatness in war strategy was not just praised by his followers but also feared by his enemies. Even the Dutch governor of East Java, Baron van Hohendorff, admitted RM Said’s brilliance in war.