Balaji Viswanath began his career as a small revenue official and became Peshwa in 1713. As Peshwa, he made his position the most important and powerful as well as hereditary. He played a crucial role in the civil war and finally made Shahu as the Maratha ruler. He sought the support of all Maratha leaders for Shahu. In 1719, Balaji Viswanath got certain rights from the then Mughal emperor, Farukh Siyar. First, the Mughal emperor recognized Shahu as the Maratha king. Second, he allowed Shahu to collect Chauth and Sardeshmukhi from the six Mughal provinces of the Deccan including the Carnatic and Mysore.
Baji Rao was the eldest son of Balaji Viswanath. He succeeded his father as Peshwa at the age young age of twenty. The Maratha power reached its zenith under him. He initiated the system of confederacy among the Maratha chiefs. Under this system, each Maratha chief was assigned a territory which could be administered autonomously. As a result, many Maratha families became prominent and established their authority in different parts of India. They were the Gaekwad at Baroda, the Bhonsle at Nagpur, the Holkars at Indore, the Scindias at Gwalior, and the Peshwas at Poona.
Balaji Baji Rao succeeded his father as Peshwa at the young age of nineteen. The Maratha king Shahu died in 1749 without issue. His nominated successor Ramraja was imprisoned by the Peshwa Balaji Baji Rao at Satara. The full control of the Maratha kingdom came under the Peshwa.
Peshwa entered into an agreement with the Mughal Emperor in 1752. According to it the Peshwa gave assurance to the Mughal Emperor that he would protect the Mughal Empire from internal and external enemies for which the Chauth of the northwest provinces and the total revenue of the Agra and Ajmer provinces would be collected by the Marathas.
Thus when Ahmad Shah Abdali invaded India, it became the responsibility of the Marathas to protect India. The Marathas fought very bravely against Ahmad Shah Abdali in the Third Battle of Panipat in 1761. But they got defeated. Many Maratha leaders and thousands of soldiers died in this battle. Balaji Baji Rao also died on hearing the sad end of this battle. Also, this battle gave a death blow to the Maratha power. Thereafter, the Maratha confederacy weakened due to internal conflicts among the Maratha chiefs.
After the decline of the Mughal Empire, the Marathas emerged a great power in India but they could not succeed in preventing the establishment of British power in India. The important causes for the downfall were that there was lack of unity among the Maratha chiefs like Holkar, Scindia and Bhonsle. Also, the superiority of the British army and fighting methods ultimately won.