Early conquests In October 1611, Islam Khan led an army consisted of 1,000 cavalry, 5,000 musketeers, 300 elephants and 300 or 3000 war boats, besides the entire navy of Musa Khan and other zamindars. The Mughal forces under Islam Khan's trusted officers, Shaikh Kamal and Shaikh Abdul Wahid, advanced with the main land army from Dhaka to Hasanpur, situated south of
Bokainagar and established camp there. Ihtimam Khan, commanding the fleet, and Mirza Nathan later joined the land army via
Egarosindur. Due to seasonal flood the combined land-naval assault on Bokainagar failed. With the naval component unfeasible, Islam Khan shifted to a land-based attack. Under Islam Khan's orders, Shaikh Kamal and Abdul Wahid marched from Hasanpur to Bokainagar, while Ghiyas Khan stayed at Shah Bandar with the entire fleet, ready for any emergency. Hearing Islam Khan's campaign against Khwaja Usman, Anwar Khan of
Baniachang voluntarily surrendered to the Mughals. Anwar was allowed to retain his territory and ordered to march with his fleet against Usman. At Egarosindur he entered into a plot with imperial officers
Mahmud Khan, Bahadur Ghazi, Islam Quli and Raja Ray against Islam Khan. The conspiracy failed before it could be carried out. Anwar subsequently fled to Baniachang. Islam Khan dispatched Raj Satrajit and
Mubariz Khan against Anwar. The superior Mughal forces under Islam Khan quickly overwhelmed Afghan resistance, leading to divisions within Khwaja Usman's ranks. Two Afghan chiefs, Nasir Khan and Dariya Khan of Tajpur, defected to join the imperial side. Alarmed by these desertions and fearing further losses, Usman evacuated Bokainagar and withdrew to Sylhet, seeking refuge with
Bayazid Karrani. By the end of November 1611, the imperial army captured the
fort of Bokainagar. Islam Khan then carried out campaigns against Khwaja Mahli and Khwaja Mumriz of
Taraf, Pahlwan, the zamindar of Matang as well as Anwar Khan. Anwar Khan who fled to Baniachang offered naval battle to Raja Satrajit. Failing to stand against the mighty army he sued peace. Islam Khan then sent Haji Shamsuddin Baghdadi with a strong force against the Afghan zamindars of Matang and Taraf. First Haji Shamsuddin captured the fort of Taraf after heavy fighting. Next he marched against Matang. Pahlwan deciding to fight, charged upon Haji Shamsuddin and killing him in the encounter. Shamsuddin's adopted son Qurban Ali gathered the troops and made a counterattack upon Pahlwan, killing him in the process. Thus, both Taraf and Matang were annexed to the Mughal Empire.
War with Khwaja Usman In January 1612, Islam Khan renewed his campaign against Usman. He simultaneously directed campaign against Usman in Uhar and Bayazid in
Sylhet. A force was composed under Shuja'at Khan consisted of large cavalry and infantry, including 500 picked cavalries of Islam Khan and 4,000 musketeers while fleet and war-boats under Ihtimam Khan and Sona Ghazi zamindar of Sarail respectively. Shaikh Kamal with 1,000 picked cavalries of Islam Khan, 4,000 musketeers, 100 elephants and entire fleet seized from Musa Khan, was given the command of the expedition against Bayazid. After long marching Shuja'at Khan finally reached at fort of Taraf. The forces against Bayazid also had generals like Mubariz Khan, Tuqmuq Khan,
Mirak Bahadur Jalair and Mir Abdur Razzaq.
Battle of Daulambapur On 4 February 1612, the Mughal imperial forces formed their battle array with Shuja'at Khan commanding the centre, assisted by Mutaqid Khan and Ihtimam Khan; the van was led by Mirza Nathan with support from Sayyid Adam, Shaikh Achha, Mirza Qasim, and Sona Ghazi; the right wing was entrusted to Iftikhar Khan, the left wing to Kishwar Khan, and the advance reserve to Shaikh Qasim. Islam Khan sent Abdus Salam to Shuja'at Khan with 1000 cavalry as reinforcement. Usman hearing the Mughal advance marched from his capital with a large army. He personally led the centre with 2,000 picked cavalry, 5,000 infantry, and 40 war-elephants; Khwaja Wali commanded the left wing with 1,000 cavalry, 2,000 infantry, and 30 elephants; Shir-i-Maydan held the right wing with 700 cavalry, 1,000 infantry, and 20 elephants; the van was entrusted to Khwaja Malhi, Khwaja Ibrahim, and Khwaja Daud with 1,500 cavalry, 2,000 infantry, and 50 elephants. According to Mirza Nathan, the Afghan army had about 5,000 cavalry, 10,000 infantry and 150 elephants. On 12 March 1612, a decisive battle unfolded at Daulambapur between the Mughal imperial forces and Afghan forces led by Khwaja Usman. The Mughals began with a false alarm that disrupted their vanguard, leading to chaos. The Afghans exploited this, defeating the imperial right wing and killing commander Iftikhar Khan, while also crushing the left wing and killing Kishwar Khan and officer Sayyid Adam. The Mughal vanguard commander Mirza Nathan was severely wounded, and the imperial center under Shuja'at Khan was broken. Mirza Nathan mistakenly killed his own ally Shaikh Achha in the chaotic conflict. Afghan victory seemed assured until Mughal horseman Shaikh 'Abdul Jalil shot Khwaja Usman through the eye, killing him. Though Usman killed his attacker, he died from the wound, and the Afghans, losing their leader, abandoned the field. The battle of Daulambapur ended in a dramatic reversal, with the Afghans fleeing despite their earlier dominance. The Afghans took Usman's dead body to Uhar and buried in a hidden tomb and his wives, daughters, except one married to Daud were put to death and also buried beside him.
Conquest of Sylhet Islam Khan reinforced Shaikh Kamal with Bihar troops and supplies to proceed against Bayazid in Sylhet. Shaikh Kamal reached the
Surma River near fort of Sylhet and began devastating raids to force submission. Bayazid dispatched his brother Ya'qub at the head of a large number of Afghan chiefs to build a fort check the invaders. Raja Satrajit and others were ordered to make a fort opposite to that of Ya'qub. Satrajit crossed the Surma River and captured the fort after a week of fighting. Raja of
Kachar strengthened Bayazid and Ya'qub with a large force. Raja Satrajit could not withstand the renewed assault, quickly surrender the captured fort and retreating across the Surma River to new fortifications. After further fierce fighting that strained the imperial forces, news of Khwaja Usman's defeat broke the morale of Bayazid and his men. He left Sylhet to Mubariz Khan and proceeded to Dhaka with Shaikh Kamal and officially submitted to Islam Khan. Thus, Sylhet was annexed to the Bengal Subah, and administrative arrangements were made. == Aftermath ==