Bengal Nawab’s short-sightedness, negligence, ignorance and lack of contact with other world cost the state dearer. They did not firmly put down the increasing tendency of the English. After 1707 EIC had started to use military force, or to threaten its use, to get its demands accepted.
Nawabs were having the power to deal with the Company’s threats, but they continued to underestimate the EIC power. They failed to see that the English Company was no mere company of traders but was the representative of the most aggressive and expansionist colonialism of the time. If they would have known the devastation caused by the Western trading companies in Africa, South-East Asia, and Latin America would have got alert and acted differently.
They had neglected to build a strong army and paid a heavy price for it. For example, the army of Murshid Quli Khan consisted of only 2000 cavalry and 4000 infantry. Alivardi Khan was constantly troubled by the repeated invasions of the Marathas and, in the end; he had to cede a large part of Orissa to them.
In 1756-1757 Siraj-ud-daula, the successor of Ali Vardi Khan, was defeated by EIC in Battle of Plasey and credit goes to absence of strong army. Failed to check the growing corruption among their officials. Even judicial officials, the Qazis and muftis, were taking bribes.