Operation Searchlight was a planned military pacification carried out by the Pakistan Army to stifle the Bengali nationalist movement in Bangladesh, then East Pakistan, in the March of 1971. The plan was to take control of the major cities on 26th March, and then eliminating all opposition, political or military, within one month.
The prolonged Bengali resistance was not anticipated by the Pakistani Army. The main phase of Operation Searchlight ended with the fall of the last major town in Bengali hands in mid May.
This operation began what is known in the western world as the 1971 Bangladesh atrocities. This systematic killing of Bangladeshis only served to fuel their rage which ultimately resulted in the secession of East Pakistan later in the same year. By the end of the War of Liberation, in the space of a short nine months, 3, 000, 000 Bangladeshis were murdered, and 200,000 Bangladeshi women were raped. Trials of war criminals still continue today, and most are still at large.
In 16th December, 1971, the Pakistani Army unconditionally surrendered to the joint command of the Indian Army and the Mukti Bahini (combined forces of the Bangladeshi Army and local militia).
Full name of the poem is Operation Searchlight: Birth Of A Nation.
I hope that brief note helps.