In 1323, the Ottoman principality conquered Karamürsel. Thanks to this conquest, the Marmara Sea was reached. In 1324, the Ottoman principality asked for help from the western neighbor Karesi principality. In line with this aid, twenty-four ships commanded by Mürsel Bey were sent. With this force, the Ottoman principality met the seas. The first step in creating a strong naval force was thus taken.
Mürsel Bey drew attention with his maritime knowledge. Also, he became famous in a short time for his heroism and courage in clashes in the seas. Along with this reputation, he was given the nickname Kara to express courage and assertiveness. Some sources reported that its name is Mürsel Alp. However, it was written in history as Karamürsel Bey with golden letters.
The Ottoman principality reached a certain dominance in East Marmara in a short time. Karamürsel Bey was the architect of domination. He established a navy consisting of light and fast ships named after him. Thanks to this navy, Marmara was taken under control. Besides, the fleet of Karamürsel Bey kept the entrance of the Gulf. Thus, Byzantium became unable to send aid to Izmit over the sea. After this domination, the Ottoman principality started to work to institutionalize the naval power. For this purpose, the first Ottoman shipyard was created in Karamürsel in 1327. The first Ottoman warship also completed its construction here. The Ottoman navy was hierarchically commissioned. The person who commanded the Navy was called Derya Bey.
Karamürsel Bey was the first Derya Bey of the Ottoman state. It succeeded in printing its name among the earlier Turkish sea history. It made history as the first admiral of the Ottoman state and the first shipbuilding engineer. He passed away after signing many principles. After their death, they gave their name to the Karamürsel district located between the cities of Izmit-Bursa. They buried him here. He stated that the place he wanted to be buried in his will was a place that overlooks the sea. By this will, he was buried in the proper place. Karamürsel Bey monument was built by the Karamürsel municipality. This monument was opened on July 4, 1976. There is an inscription made of white marble under the monument. In this inscription, the life of Karamürsel Bey is briefly described.