Learn Farsi: می‌خواستیم پیام راجع به عملیات را رمزگشایی کنیم. - We were going to decrypt the message regarding the operation.

The object marker را attaches to the very end of the entire noun phrase that serves as the direct object. Here, the complete direct object is پیام راجع به عملیات (the message regarding the operation). Even though پیام is the head noun, را must wait until the whole descriptive phrase is finished.

Why is می‌خواستیم translated here as "we were going to" rather than "we wanted to"?

While می‌خواستیم literally means "we wanted," the past continuous form of خواستن (to want) is the standard way to express past intention in Farsi. When followed by a subjunctive verb like رمزگشایی کنیم, it frequently translates more naturally to "we were going to" or "we were about to" do something.

How does the compound word رمزگشایی break down?

It is made of رمز (code, password, or secret) and گشایی (opening or untying, derived from the present stem of گشودن). Combined with the auxiliary verb کردن (to do), the compound verb رمزگشایی کردن literally means "to do code-opening," which is the standard term for decrypting or decoding.

I've learned that the ـات ending indicates an Arabic plural. Is عملیات plural here?