Learn Italian: Temevamo che il traditore avesse rivelato la missione. - We feared that the traitor had revealed the mission.

The main verb temevamo (we feared) is in the past tense. Because the fear is about an event that happened even earlier (the traitor had already revealed the mission before we started worrying), we must use the pluperfect subjunctive to show this step further back in time.

What triggers the use of the subjunctive mood in this sentence?

The verb temere (to fear) is the trigger. Verbs expressing emotion, worry, or subjective feelings followed by che (that) require the subjunctive in the dependent clause because they state a personal reaction rather than an objective fact.

Why is the helping verb avesse used here instead of fosse?

The verb rivelare (to reveal) takes a direct object (here, la missione). Verbs that take direct objects use avere as their helping verb in compound tenses. Therefore, we use the imperfect subjunctive of avere (avesse) combined with the past participle (rivelato).

Why is the main verb temevamo in the imperfect tense rather than the passato prossimo?

The imperfect tense is used for temevamo because it describes an ongoing state of mind in the past. It sets the background scene: we were in a continuous state of fearing, rather than describing a single, sudden moment of fright.