This letter was written perhaps six months after the earlier letter. This second letter seemed to have been prompted by three developments: 1) there was news of increasing persecution; 2) to deal with reports of a pseudo-Pauline letter and other misrepresentations of his teaching about eschatological matters, and 3) to give detailed instructions covering the disciplinary steps the church should take in correcting those who refuse to work (3:6-15).
There is a huge focus on end-time events in both of the letters to the Thessalonians. But I Thessalonians, the focus is on Christ coming FOR His Church, whereas in II Thessalonians, the focus is on Christ coming WITH his Church in judgment on the unbelieving world. Chapter two is key in that it corrects the mistaken notion that the Day of the Lord had already occurred.
Here is an outline for II Thessalonians:
I. Salutation or Introduction (1:1-2)
II. Paul offers commendation and comfort regarding Persecution (1:4-12)
III. Paul corrects and challenges regarding the Day of the Lord (2:1-17)
IV. Paul commands and convicts regarding Idleness (3:1-16)
V. Paul concludes with a benediction and greeting (3:16-18)