Dandanakan War (1040)
On the other hand, Sultan Mesud had finally perceived that Seljuk people posed a dangerous threat for his state and he organised an expedition upon them. Finally, Sultan Mes’ud could defeat the Seljuk people in the first two wars (1039). However, this was not an absolute victory for the Gazneli State that could be considered enough to establish dominion on all of Seljuk people. Therefore, they proposed the state of peace to Sel….. According to this proposal accepted by Sel….; the Gazneli army would penetrate into Heart, the cities and borders of Nesa, Baverd, and Fevare would be surrendered to Sel…. and Sel…. would evacuate the cities of Nisabur, Serahsand Merv that they had invaded.
The reason for the acceptation of this state of peace by the two parties was to rest and to prepare for another war. Seljuk people violated the conditions of the state and started their raids towards the lands of the Gazneli State. Sultan Mes’ud set in motion towards Sel…. again. There were various wars that continued between Sel…. and Gazneli State, but the most significant and the greatest one took place near the castle of Dandanakan within the environs of Merv. Seljuk people achieved a firm result against the army under the command of Sultan Mes’ud and they defeated the Gazneli State in a crushing manner (24th May 1040). Pursuant to the victory of Dandanakan War, Seljuk Beys gathered all together and declared that Tugrul Bey was the “Emir of Khorasan”. from that date on, they established a fully independent state in Khorasan and took the first step in the establishment of a great empire. Furthermore, as required by the traditions of the period, they sent “fetih-name” (statement of conquest) to the neighbouring rulers that expressed their victories.
Seljuk leaders convened in a Council that gathered in the city of Merv in the same month and took some important resolutions. According to a resolution that they had taken in this meeting, they declared that they were submissive to the Abbasi Caliph Kaim bi-Emrillah and they would establish justice in Khorasan. Afterwards, Sel…. shared the countries that they planned to capture in accordance with the ancient Turkish traditions similarly. According to these shares, Tugrul Bey would take Nisabur in his capacity as “sultan” and go to the west and to Iraq. Cagri Bey would take the region between Ceyhun and Gazne providing the centre of Merv in his capacity with the title as “melik” (ruler). Similarly, Musa Yabgu would take Bust, Herat and the environs of Sistan. The princes pertaining to the same dynasty were charged with the duty to capture one region per each. Seljuk State attempted to organise their conquests based on this principle and they realised this plan swiftly.
Cagri Bey had had great victories in the wars waged again Gazneli State and he repelled them from Khorasan. He defeated one army of the Gazneli State and captured the city of Belh (the autumn of the year 1040). They advanced towards Harezm together with Tugrul Beyand defeated Shah Melik that was their old enemy. They took the revenge of the raid that they suffered in the past and they subdued the Harezm country to Seljuk State (1043). Then, Cagri Bey maintained his success through the help of his son, Alp Arslan and defeated the Karahanli State. He concluded a successful agreement with the Karahanli State providing that the domination of Seljuk State would be recognised in the regions that the Sel…. captured and the Karahanli State would not attack to these regions (1050). Cagri Bey had also concluded an agreement with Gazneli Sultan Ibrahim providing that Hindikus Mountains would be the borders between the two states (1059). This agreement between the two states was valid and effective for nearly a century. Cagri Bey who had played a significant role in the foundation of Seljuk State died at the age of seventy in the city of Serahs (1060).
Musa Yabgu who was the eldest member of his family invaded Herat pursuant to the Dandanakan War (1040). He dominated in the region of Sistan and mostly resided in Heart. However, it has been observed that he was not as successful as the other members of the dynasty. As a matter of fact, he rebelled against the Sultan Alp Arslan in the year of 1064. As a result, he was caught in the castle of Herat and brought to Alp Arslan and his political life ended thereof.