Timing of Battle of Plassey: Ahmed Shah Abdali had attacked Delhi in 1756/57, sacked the City and killed its innocent residents. He sacked a few other cities nearby and was planning to invade Bengal. Siraj sent bulk of his troops under Raja Rajnarain to protect Sube Bangal's western border with Audh from a possible attack.During this precarious period, a farcical battle was conceived by Robert Clive and the local conspirators.
Number of Nawabi Troops: It is said the Nawab took 50,000 troops to the battle field. But, in reality he was not directly cotrolling all those troops. One knows how the chain of command is maintained in the military, specially during war time. A General cannot just overpass the superior officers and order the lower ranked commanding officers directly, because it breaks the chain of command.
Generals Mir Zafar, Yar Latif and a few Hindu Rajas were controlling about 16,000 to 18,000 troops, who were standing idle because their superiors did not order them to move. They were waiting at the flank and almost behind the main troops led by Siraj.
Battle Field Activities: Siraj was certainly aware of a duplicity. Only he was binded by his fate and he was helpless, too. He was so helpless that he had to trust Mir Zafar and believe what he promised. Mir Zafar was called in his camp. The young innocent Nawab put his Royal Turban on his feet and begged tearfully to move his troops. The crook Gaddar bowed and promised intervention after the lunchbreak.
On his words, Nawab declared a cease fire. There was no senior advisors in the Nawab camp to protest Mir Zafar. Raja Raj Narain and many other loyals were sent to face Ahmed Shah Abdali in the west. Their presence could have balanced the power of Mir Zafar in the battle field.
In order to offset a possible attack from behind/flank he had to place almost 18,000 troops that faced Mir zafar's troops. There were other groups of troops who were not engaging the enemy, but were protecting the camp of Nawab. The total number of Nawabi troops that were fighting the British were about 5,000. This number was still quite large comparing to the size of enemy.
Two Important Factors: But, two important factors contributed to the outcome of the battle. Loyal General Mir Madan received a fatal hit by a cannon ball. And during the lunch ceasefire requested by Mir Zafar, a heavy shower dampened the ammunition of Bengal army. Although the artillery was manned by a group of French gunners, they did not forsee a rain, and thus did not take with them all the sheets needed to cover them.
Opportunist Mir Zafar: Historians say that Mir Zafar wanted to side with the British only if they proved winner by their own capability, but would side with the Nawab if his troops were on the verge of winning. He was such an opportunist. But, the rainfall decided the fate of that battle.
Rainfall Decided the Fate: When the battle re-started, the wet local cannons could no more be fired. On the contrary, the British cannons were firing hot balls. Troops sensed a conspiracy because the troops under Mir Zafar was not moving. Mir Madan was already killed, the petty officers were without a suitable commanding officer. Nawab side was in a complete mess.
In such a situation, the troops started to leave the battle field in groups. So, the fate of Bengal and also the entire Hindustan was decided by this heavy and cursed monsoon rainfall of Bengal that caused us untold misery during the 190 years of slavery under British.