What key concern does Paul address in his second letter to the Thessalonians?

In his second letter to the Thessalonians, Paul addresses the confusion and fear among the believers that the Day of the Lord had already occurred. He reassures them that certain events must take place before Christ's return and emphasizes the importance of maintaining faith and an understanding of the timeline of eschatological events. This concern is particularly evident in the context of false teachings that had emerged, suggesting that the Lord's return was imminent or already had taken place. By clarifying this issue, Paul aims to restore hope and encourage the Thessalonians to stand firm in their faith, assuring them that they will not miss the promised return of Christ.