Next, we enter the Mataram kingdom period. Mataram attempted to weaken the Surabaya principality by attacking Surabaya's allies first. Mataram's strategy to attack Surabaya's territory was aimed at cutting off the logistics route to Surabaya. Sultan Agung's efforts never succeeded in bringing Surabaya down. Although Sultan Agung always failed to conquer Surabaya, he never gave up. After several decades, Sultan Agung managed to subdue the areas around Surabaya, such as Tuban in 1619 and Madura in 1624, but he still could not bring down the Surabaya principality. Eventually, Mataram's prolonged expedition resorted to sabotage tactics, namely by polluting the Kalimas River with animal carcasses, human remains, and palm fruit. Finally, the Surabaya principality surrendered to Mataram on October 27, 1625.