Sunyatphaa also Udayaditya Singha was the king of Ahom Kingdom from 1670 CE to 1672 CE. After his elder brother Swargadeo Chakradhwaj Singha died in the middle of Ahom-Mughal war, Udayaditya Singha succeeded to the throne. His reign witnessed the end of Ahom-Mughal war, which started during the reign of Chakradhwaj Singha, when the Mughal army led by Rajput prince, Ram Singh I of Amber, was decisively defeated by the Ahom forces led by Ahom commander Lachit Borphukan in the Battle of Saraighat. The later part of his reign was characterized by the failure of military expedition against the Dafala tribes and the influence of Paramananda Sannyasi, a saintly figure from Brindaban, over Udayaditya Singha. Udayaditya's over exerted devotion towards Paramananda Sanyasi, aroused dissatisfaction among the nobles, which ultimately caused his deposition and execution. His reign was followed by a series of political anarchy and internal disturbances in the Ahom kingdom which continued till the accession of Gadadhar Singha in 1681 CE.
Ancestry and early life
Udayaditya Singha was the second son of Namrupia Raja, the grandson of Sureng Deoraja, great grandson of Ahom king Suhungmung. His grandfather Sureng Deo Raja was the founder of the Charingia branch of Royal Ahom Dynasty. Sureng Deo Raja was a valliant warrior, who fought many battles in military expedition against Chutiya Kingdom and Kachari kingdom during the reign of his father Suhungmung. He also fought against the invading forces of Koch kingdom led by Chilarai during the reign of his elder brother Suklenmung and his nephew Sukhaamphaa. The early name of Udayaditya Singha was Maju Gohain. When his elder brother Chakradhwaj Singha ascended the throne, Maju Gohain was appointed as Charingia Raja, a post usually held by the heir apparent to the throne.
Accession
Swargadeo Chakradhwaj Singha died of dropsy in April 1670 CE. The heir apparent to the throne, Maju Gohain was proclaimed as the king of Ahom Kingdom. The Hindu priests and Brahmins named him as Swargadeo Udayaditya Singha, while the Tai-Ahom priests conferred on him the title Sunyatphaa.
Reign
War with the Mughals
Udayaditya Singha ascended the throne at a time when the Ahom-Mughal war that started during the reign of his elder brother Swargadeo Chakradhwaj Singha was at its climax. The Mughal army led by the Rajput king Raja Ram Singh I of Amber was desperately trying to conquer the military outpost of Guwahati, while the Ahom forces led by Lachit Borphukan and Atan Burhagohain was bravely defending it against all odds. Raja Ram Singh I sent a proposal to the Lachit Borphukan, that if the Ahoms surrender the garrison of Guwahati in favour of Mughals, he gave his word that the Mughals will respect the boundary of Ahom kingdom which was set according to the treaty of Asura Ali in 1639 CE. The long continuance of hostilities without any decisive result produced some discontent in the Ahom camp. The demand of Ram Singh I thus, received a more encouraging response from Lachit Borphukan and his lieutenants. The proposal was sent to Swargadeo Udayaditya Singha for final decision. The king held consultation with all the nobles. While most of them are in favour of the proposal, the Prime Minister of Ahom kingdom, Atan Burhagohain opposed this proposal stating that the resistance which they had offered to the enemy and which caused such loss of men and provisions was absolutely meaningless if it was followed by their voluntary surrender of Guwahati. He also characterized the promises made by Ram Singh I as a highway made of ashes as they might not be accepted by the Mughal Emperor Aurangzeb, or by the next Mughal commander who will succeed Ram Singh I. Swargadeo Udayaditya Singha confirmed the views of the Premier Atan Burhagohain and directed the commanders to bring the war to a victorious conclusion.