Rani Tarabai, or the (dowager) Queen Tarabai, was
the wife of Chatrapati Rajaram Maharaj, and the daughter-in-law of
the great Chatrapati Shivaji Maharaj.
Born in 1675, she was also the niece of
Shivaji's wife, Soyrabai (Rajaram's mother) and the daughter
of Hambirao Mohite, the famed Sarsenapati (commander-in-chief) of
the Maratha army.  
Fight against the Mughals
Thanks to her father's upringing for her and the
fact that she was well versed in the art of warfare, Tarabai herself planned and supervised military expeditions.
In 1705, Nemaji Shinde entered Malwa (Madhya Pradesh) and ravaged it
while Khanderao Dabhade raided Mughal territory as far as Ahmedabad (Gujrat).
In 1706, Ramchandra Bavdekar bribed the commandant
of Fort Panhala and it was passed on to the Marathas (as was Pawangad). Parshuram Trimbak and Annaji later retook Satara
and then Parali. Shankar Gandekar retook Sinhagad, Torna and Rajgad.
Dhanaji Jadhav, the commander-in-chief, led many expeditions against
the Mughals, along with other able Maratha commanders such as Udaji
Pawar and Haibatrao Nimbalkar, and caused serious damage to the
Aurangzeb too had aged. For a man rarely accustomed to failure, he
had to bear the ignominy of repeated failures and a string of bad
news reports coming from Maratha territory.
In 1707 (at Khulatabad near Aurangabad), Aurangzeb, the Mughal
emperor, died a bitter man.
Advent of Shahu
After Aurangzeb's death, the Mughals (under Prince Azam) released Prince
Shahu, the son of Sambhaji (and grandson of Shivaji) from their
prison. The idea was that Maratha ire against the Mughals would be
alleviated and also that there should be an element of dissension in the Maratha
ranks, leaving the Mughals free to fight their own succession
battles (between Prince Azam and Shah Alam, Kambaksh etc).
Tarabai however refused to acknowledge Shahu as the real king and
insisted on her son becoming her successor. She even called Shahu an imposter.
But with Shahu's arrival, many Maratha commanders left Tarabai's side
and joined Shahu. They felt Shahu being the son of Sambhaji was
their natural ruler (and Rajaram and Tarabai were only temporary
rulers in the absence of the real king).
After a few unsuccessful battles and facing the regular desertion
of her closest aides, Tarabai accepted defeat and reluctantly agreed to
accept Shahu as the rightful king of the Marathas.
Shahu also allowed his aunt to retire to the province
of Kolhapur, where she set up her independent throne in 1713.
Tarabai outlived her son.
Tarabai's power politics
After the death of Shahu in 1749, Tarabai supported the succession
of Ramraja (Tarabai's putative grandson and later adopted by Shahu)
to the Maratha throne. Through Ramraja, she tried to exercise
control over the affairs of the Maratha kingdom. She even tried
unsuccessfully to remove the Peshwa Balaji Bajirao from his post,
as she found him an impediment which was challenging her power.
Later, finding Ramraja difficult to control, Tarabai imprisoned him.
There was a brief power struggle between the Peshwa Balaji Bajirao
and Tarabai. But eventually the power of the Peshwas prevailed. The
old queen agreed to a compromise whereby she would accept the
power of the Peshwas, leaving them in sole control of the Maratha
kingdom. In return the Peshwa would allow Tarabai independent
control over her principality. Also, Tarabai was to declare that Ramraja
was not her grandson, as she initially claimed, but an impostor
she had used to succeed the childless Shahu.
Ramraja remained Tarabai's prisoner to the last.
Tarabai died in 1761.