In October 1528, Sultan Mohammad of Bihar died, and his queen, Dudu Bibi, assumed the role of
regent. Sher Shah was appointed as her deputy governor, allowing him to begin consolidating his position in the region through a myriad of military and administrative reforms. These reforms significantly strengthened his position, making him one of the most influential Afghan leaders in India. In 1529, Sher Shah anticipated joining Mahmud Lodi, the younger brother of
Ibrahim Lodi, in his
insurrection against the Mughals that rallied most of the significant Afghan leaders in India. Sher Shah, however, recognized the division among the Afghans and Mahmud's incompetence, thus refusing to aid Mahmud. Intending for the unification of all Afghan leaders, Mahmud marched with his army to Sasaram, persuading Sher Shah to join the rebellion. Hesitatingly, Sher Shah accompanied the expedition with his own set of men, and the insurrection initially succeeded, capturing
Ghazipur and
Banaras. However, upon the arrival of Mughal forces, Mahmud Lodi abandoned the army. After this, many Afghan nobles including Sher Shah submitted to Babur. In early 1530, the death of Dudu Bibi enabled Sher Shah to become the regent for Jalal Khan, effectively making him the de facto ruler of Bihar. Despite his growing power, many of the Lohani nobles opposed Sher Shah's dominance. Although he offered to share power, the Lohani nobles rejected his proposal and instead fled to Bengal with Jalal Khan, seeking the support of
Nasiruddin Nasrat Shah, the
ruler of the
Bengal Sultanate. Consequently, Sher Shah became the sole ruler of
Bihar. However, he did not adopt any grand titles, preferring to style himself as Hazrat-i-Ala.
Acquisition of Chunar (1530) Taj Khan, the governor of
Chunar, was assassinated by his stepson. In the aftermath, his wealthy widow, Lad Malika, sought a protector to secure her position. Recognizing Sher Shah's growing influence, she agreed to marry him. Through these negotiations, which were kept secret from Taj Khan's sons, Sher Shah gained control of Chunar. This acquisition significantly bolstered Sher Shah's power and influence in the region, as he now controlled a significant fort and a large treasury.
First conflict with the Mughals (1530–1532) The death of Mughal Emperor
Babur in December 1530 saw the Afghan insurrection rejuvenated, and Mahmud Lodi again returned. Sher Shah immediately ignored Mahmud's attempts of garnering Sher Shah's aid until he was promised all of Southern
Bihar. After further being visited by Mahmud, Sher Shah acquiesced. The combined Afghan forces marched on
Banaras and
Jaunpur, with Junaid Khan withdrawing to Agra. The Afghan forces followed up their victories by seizing
Lucknow. Humayun, entrenched in a siege of
Kalinjar, immediately withdrew, crossing the
Ganges and began a battle against Mahmud Lodi at Dadrah in 1531. The Afghan forces were decisively defeated, and the coalition was shattered. Mahmud Lodi fled to
Orrisa, while Sher Shah emerged on top by keeping Southern Bihar. Humayun followed up his victory by
besieging Chunar, a fortress owned by Sher Shah, in September 1532. The siege continued for over four months to no avail. In order to make peace, Sher Shah offered his loyalty to the Mughals on the condition that he remained in control of Chunar, offering to send his third son, Qutb Khan, as hostage. Humayun accepted and lifted the siege in December 1532, returning to
Agra due to the rising threat of
Bahadur Shah, the ruler of the
Gujarat Sultanate. Humayun did not wish to split up his forces under the command of a noble to continue the siege, as this would split his strength, additionally giving reason for peace to be established.
Lohani conflict and Bengal campaign (1533–1537) Makhdum Alam, the administrator of
Hajipur, refused to recognize
Ghiyasuddin Mahmud Shah as the
Sultan of Bengal, accusing him of assassinating the previous Sultan,
Alauddin Firuz. He formed an alliance with Sher Shah, who saw this as an opportunity to crush the power of the Lohani nobles allied with Mahmud Shah. Mahmud Shah sent several expeditions against Sher Shah, which were all defeated. Makhdum Alam however, was killed, and his estates fell to Sher Shah upon his death. In 1534, Mahmud Shah sent an army of
artillery,
cavalry and
infantry under Ibrahim Khan to conquer Bihar, with Jalal Khan accompanying the campaign. However, Sher Shah launched a sudden attack on the combined forces of the Lohani chiefs of Bihar and Mahmud Shah of Bengal, defeating them at Surajgarh in March 1534, winning a decisive victory. Ibrahim Khan was killed during the battle, and Jalal Khan was forced to retreat to Bengal. Following the victory, Sher Shah consolidated his control over Bihar. Between 1536 and 1537, Sher Shah followed up his victories by invading Bengal and defeating Mahmud Shah numerous times, occupying all lands west of the
Teliagarhi pass. Mahmud Shah repeatedly requested the
Portuguese to aid him, which they did by fortifying the Teliaghari and
Sakrigali passes. Sher Shah, however, out-flanked the combined armies and reached
Gauda by way of
Jharkhand. Mahmud Shah immediately capitulated, and was forced to pay over 13,000,000 gold coins, and cede territory up to Sakrigali.
Second Bengal campaign and conflict with the Mughals (1537–1540) Eager to conquer the Bengal Sultanate, Sher Shah prepared for another invasion, and an opportunity came when Mahmud Shah failed to send annual tribute, forcing him to seek refuge in Gaur and frantically ask
Humayun for aid. In response, Humayun mobilized a
Mughal army in July 1537, and advanced towards
Chunar. The Mughals reached the fort in November 1537 and laid siege to it. The siege lasted over six months before the fort finally fell. Following this, Sher Shah began a second invasion into Bengal, seizing
Rohtasgarh in March 1538 through stratagem. He used Rohtasgarh to situate Afghan families and loot he obtained during the war. Following up his victory, Sher Shah besieged Gauda, which fell in April 1538. Split detachments would also be sent to conquer
Chittagong. Another force battled against Mahmud Shah led by
Khawas Khan Marwat, a general of Sher Shah, which saw Mahmud Shah decisively defeated and mortally wounded. With these victories, Sher Shah held his first coronation. After the fall of Gauda, Sher Shah offered favorable peace terms to Humayun, proposing to pay 1,000,000 dinars, and cede Bihar in exchange for control of Bengal. Humayun refused the offer, not wishing to leave Bengal's rich resources to a hostile state. Additionally, the wounded Mahmud Shah, who had entered Humayun's camp, urged him to continue the war against Sher Shah. Mahmud Shah died from his wounds soon after. Following this, Humayun marched towards Bengal to confront Sher Shah. However, the Mughal army was troubled with heavy rains, causing the loss of their baggage between
Patna and
Monghyr. Humayun eventually reached
Gauda and seized it without opposition on 8 September 1538. However, the city had been abandoned by the Afghans, and the treasury looted. Humayun remained in Gauda for months, restoring order to the city, as he was trapped with his army due to the weather. Sher Shah capitalized on this, seizing Bihar and
Varanasi, reclaiming control over Chunar, and laying siege to
Jaunpur. Other detachments of the Afghan army extended as far as
Kannauj. As a result, Humayun found himself effectively stranded in Gauda with no lines of communication. Learning of unrest in
Agra, Humayun immediately sought to settle for peace with Sher Shah. However, as he crossed the
Karmanasa River, where his army was vulnerable to attack, Sher Shah capitalized on the Mughal army's fragile state and attacked at the
Battle of Chausa. The Afghans descended on the Mughal army, which was 200,000 strong. Overwhelmed, the Mughal army was completely
routed. Humayun barely escaped with his life, with the Mughals suffering over 7,000 casualties, including many prominent noblemen. With his defeat, Humayun returned to Agra, and restored order after unrest began due to his brother,
Hindal Mirza. Humayun then began mobilizing another army and advanced against Sher Shah, who raised his own army, although being numerically inferior. The two armies met at
Kannuaj, mirroring each other across the
Ganges river. Humayun crossed the river and engaged in skirmishes with Sher Shah's forces. During the fighting, many of Humayun's nobles hid their insignia to avoid recognition by the Afghans, and several fled the battle. The Mughal army was ultimately defeated, forcing Humayun to flee. Following this victory, Sher Shah was crowned a second time on 17 May 1540, being declared the ruler of
Hindustan and adopting the epithet Sultan Adil, meaning "Just King." He further took on the name Sher Shah. ==Reign as Sur emperor (1540–1545)==