Ghiyasuddin Tughlaq, a former slave of mixed parentage–Turkish and Mongol– ascended the throne in 1320 and led successful campaigns to Warrangal, Orissa and Bengal. Within four years of his rule he extended the boundaries of Delhi up to Madurai in the south. In 1320, Ghyasuddin extended the territories of the Delhi sultanate upto Madurai. In 1321, Ghiyasuddin began work on a new fortified city of Tughlaqabad, towards east of the existing city, and shifted his capital there three years later. The fort was built on a mammoth scale with sloping bastions, 13 gates, and a citadel with three gates within. It was also connected to Old Delhi by a secret underground passage.
During Ghiyasuddin’s reign lived the great Sufi saint - Nizamuddin, and his devotee - the Persian poet Amir Khusrau. Khusrau was an accomplished musician too and his art reflected amalgamation of the Muslim and Hindu traditions. Around the time Tughlaqabad was being built, Nizamuddin was having his Baoli (reservoir) constructed, which the Sultan neglected. As the legend goes, the incensed saint prophesized that the new fort would be inhabited by nomads and eventually crumble down to ruins. Following Ghiyasuddin’s death in 1324, his successor, Muhammad Bin Tughlaq, moved back to the previous city and nomads used the fort for a while, until it was abandoned and eventually fell to ruins.
Muhammad Bin Tughluq (1325 - 1351)
Muhammad-bin-Tughlaq's experiments with his ideas of administration are noteworthy. The transfer of his capital from Delhi to Daulatbad earlier known as Devagiri. This transfer of capital involved the shifting of the army, officials, servants, tradesman, court and shift of population. This was a torture of the people who suffered greatly. The introduction of token currency brought discredit to his rule. The rampant circulation of copper coin and withdrawal of silver and gold coins brought down the value of currency. Copper coins lost its value. To overcome this the Sultan ordered exchange of silver coins for copper coins. Thus people got silver coins in abundance and copper coins were in heaps. The taxation in Doab which resulted out of the conditions of an empty treasury and the scheme which was implemented in a wayward manner made it a failure. The conquest of Khorasan which required a strong army and later disbanding it was an act of instability.
Muhammad bin Tughluq's engagements with his domestic affairs made him turn a blind eye to the Mongols who made use of his opportunity and invaded India in 1328 AD. The shifting of the capital from Delhi to Devagiri also proved advantageous to the Mongols, as they prepared for more conquests. The Sultan's ambitions plan of invading Himachal and the devastationof his army owing to inhospitable climatewas another blunder by Mohammed-bin -Tughluq. An attempt to capture Malabar in 1335 AD failed owing to the spread of Cholera in the army. In1338 Fakhruddin Mubarak of Bengal declared himself independent. In 1340 the Governor of Gujarat declared himself independent. The Sultan faced problems from the Afghans led by Hasan Gangu . In 1350 AD the province of Gujarat revolted and under Taghi. Pursuing the enemy to inflict punishment, unfortunated Mohammed bin-Tughluq died out of illness. He was succeeded by his cousin Feroz Tughlug who was delivered of a Rajput mother.
Firoz Shah (1351-1388)
Firoz Shah Tughlaq succeeded his cousin Muhammad Bin Tughlaq after his death. But he could not contain the rebellions that broke out during his reign, instead, he spent most of his time in philanthropic pursuits, such as beautification of the city, renovating his predecessors’ monuments and building schools, hospitals and wells. In 1354, Firoz Shah started construction of Firozabad on the banks of the Yamuna. The new city included three palaces and a citadel, known today as Firoz Shah Kotla, surrounded by gigantic ramparts. The Sultan also had two Ashokan pillars transported from Topra (in Punjab) and Meerut and had them planted in Delhi. They can be seen at Firoz Shah Kotla and near Bara Hindu Rao in North Delhi. Firoz Shah also built the two existing shrines - Dargah Roshan in Chiragh Delhi, and Qadam-i-Sharif in Old Delhi near Lahore Gate.