Siraj ud-Daulah was the last Nawab of Bengal. His full name was Shah Quli Khan Mirza Mohammad Haybat Jung Bahadur (Siraj-Ud-Daulah). There are varying opinions regarding his date of birth. According to many, he was born in 1732, while some believe he was born in 1733. However, the more acceptable view is that he was born in 1732. (article continues below)\
Siraj was the grandson of Nawab Alivardi Khan. Alivardi Khan had three daughters and no sons. Mirza Mohammad (Siraj Ud-Daulah) was born in the womb of Amena Begum, the third daughter of Alivardi Khan. When Siraj ud-Daulah was born, Alivardi Khan took over the rule of Patna, so he considered the birth of Siraj as a sign of good fortune and adopted the newborn as his adopted son. From then on, he grew up with the love of his grandfather.
When Alivardi khan went to war against the Marathas in 1746, young Siraj became his ally. But as he was young, Raja Janakiram was appointed as the royal representative. Siraj ud-Daulah was dissatisfied with this matter. So he secretly left Murshidabad in the name of traveling with a faithful servant. He then went to Patna and asked Janakiram to step down. But Janakiram refused to relinquish power without the permission of the Nawab and closed the gates of the fort and sent envoys to inform the Nawab about the matter. Siraj ud-Daulah attacked Janakir's fort. Upon receiving the news, Alivardi Khan came to the spot, normalized the situation and announced, ''Siraj ud-Daulah will be my successor after me, and will rule Bengal-Bihar-Orissa." 
At that time, Siraj ud-Daulah was only seventeen years old. Many of his relatives could not accept the nomination of him as the successor of Alivardi Khan. Even his aunt could not accept it. She started plotting against Siraj ud-Daulah in various ways.
Alivardi Khan died on 10 April 1756.  After his death, Siraj ud-Daulah became the Nawab of Bengal. After Siraj ud-Daulah ascended the throne, great anarchy and conspiracy started all around. Ever since he took charge of the state, the British presence in India has been on the rise.
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At first, he caught the conspiracy of his aunt Ghaseti Begum and arranged to bring her to Murshidabad. Then on 16 June 1756, Siraj ud-Daulah invaded Calcutta and on 20 June, the fort of Calcutta came under the control of Siraj. On 12th July, he returned to the capital. Shortly afterward, the king and nawab of Delhi, Shawkat Jung, sent a war charter against Siraj ud-Daulah and started a war. The British secretly tried to make friends with Shawkat Jung. Siraj ud-Daulah and Shawkat resisted the Jang and engaged in a face-to-face battle at a place called Nawab. Shawkat was killed in the battle.
Siraj ud-Daulah signed a treaty with the British on February 7th, 1757. Siraj made many sacrifices for that treaty. On 23 June 1757,  the British troops in Calcutta joined the army at Chandan Nagar. The Nawab realized that General Mir Jafar was with them. Siraj forgave Mir Jafar with the thought of capturing him and asked him to take an oath. He will swear by touching the Holy Quran that he will not allow the independence of Bengal to be tarnished even if it meant death for him. After resolving all this, he started the war with the aid of Mir Jafar, Mir Madan, Yar Latif, Roy Durlav, Mohanlal and the French general Sinfren with the responsibility of leading the army. But during the war, Mir Jafar, Yar Latif and Roy Durlov were standing where the troops had gathered.
On the other hand, Mir Madan and Mohanlal were continuing the war. When it suddenly rained in the afternoon, the gun powder of Siraj ud-Daulahs’ army got wet, but brave Mir Madan continued the battle. Suddenly, Mir Madan was killed by a bullet. Mohanlal was fighting. But Mir Jafar again betrayed and ordered his troops to return to the camp. Unable to find a way, Siraj set out for Murshidabad with two thousand troops to defend the capital. But when no one was there to help him, Siraj ud-Daulah with his wife, daughter, and servant, left the capital and reached Bhagrangola by land. Mir Jafar sent people around to capture Siraj. The Nawab's boat got stuck in the river and he came to the market near a mosque to collect food. Some people recognized him and due to their greed for money they informed Mir Kashem about Sirajs’ presence. They came and captured Siraj ud-Daulah and sent him to Murshidabad.
On 2nd July 1757, by the orders of Mir Zafar, a murderer named Muhammad Ali beg killed Siraj ud-Daulah (4). He was buried near the tomb of Nawab Alivardi Khan at Khoshbagh in Murshidabad.
 In May 1752, the nawab declared Sirajuddaulah as his successor .... http://en.banglapedia.org/index.php?title=Sirajuddaula
 Alivardi Khan died of dropsy on 10 April 1756 at the age of 80 or 80 above ... https://military.wikia.org/wiki/Alivardi_Khan
 The Battle of Plassey was fought on June 23, 1757, exactly 261 years ago...
 Siraj-ud-Daulah was executed on 2 July 1757... https://en.wikipedia.org/wiki/Siraj_ud-Daulah