She wrote: "The troops and officers included men of all faiths, including Sikhs. It is never easy to undertake security action involving a place of worship, especially in a country where religion is so easily and often used for political ends. But this place, so sacred to people of the Sikh faith, had been converted by terrorists into a base of operations".
Stating that "we did not know that arms were being collected there", Gandhi wrote that vast and sophisticated amount of weapons were discovered and many bore foreign marking.
"We also found some foreign nationals among the desperadoes. For months a reign of terror was unleashed from the temple complex, holding all Punjab to ransom. We had no choice but to send an army unit which exercised the utmost restraint, using a minimum of force".
Gandhi concluded the two-page letter by stating that although the "hard core of the terrorists within has been liquidated", there was a difficult period ahead.
"Many in the Sikh community have been shaken by this traumatic event. The process of healing and reconciliation will take time but we shall persevere," she wrote.
Gandhi was assassinated on October 31, 1984.