Trunajaya's North Coast offensive

The Trunajaya rebellion began in 1674 as Trunajaya's forces conducted raids against the cities under Mataram control.[2] In 1676, a rebel army of 9,000 invaded East Java from their base in Madura, and took Surabaya – the principal city of East Java – shortly after.[1] Mataram King Amangkurat I sent a large army to oppose him under the Crown Prince (later Amangkurat II), but this army was decisively defeated on 13 September at the Battle of Gegodog in northeast Java.[3] After Gegodog, the Javanese north coast was open to Trunajaya's forces.[3]

The rebel forces quickly proceeded westwards after the victory.[3] The Javanese northern coastal region – also known as the Pasisir – contained many trading towns, such as Surabaya (already taken by Trunajaya before Gegodog), Tuban, Juwana, Pati, Jepara, Semarang and Kendal.[4]

Trunajaya's forces met their first significant resistance in Jepara. In response to the rebellion, Amangkurat had installed a military man, Angabei Wangsadipa as governor in Jepara overseeing the entire northern coast.[2][5] Subsequently, the town's defenses had been reinforced and additional cannons had been placed.[2] Jepara's defender also had help from a Dutch East India Company (VOC) force of 200 men, who was reinforced by sea "just in time".[3][5] They arrived there on 20 November 1676 and begin besieging the city.[6][7] The joint Mataram-VOC defense, as well as with quarrel between the Madurese and Makassarese elements of the attackers, caused the attack to ultimately fail.[7][3][5]

After failing to take Jepara, Trunajaya's captains – whose forces were augmented by Javanese defectors eager for booty – attacked other towns along the coast.[3] The attacks were made easy because many towns had their fortifications dismantled during or after their conquest by Mataram's Sultan Agung about five decades before.[3] Trading-towns were laid in ruin and ships were taken over to carry out further attacks.[3] According to H. J. de Graaf, Mataram troops conducted "courageous" defenses of Kudus and Demak, but they ultimately fell.[3] In 5 January 1677, Trunajaya reached as far west as Cirebon and took the town, after other coastal towns (except Jepara) had been taken or forced to acknowledge Trunajaya's authority.[3][8] VOC forces in their Batavia headquarters prevented a further westward advance.[3]