The companion Paul mentions in verse 1 as “Silvanus” was almost certainly the Silas of Acts 17:1-10, as this is a shortened form of the longer name (a “nickname,” as Jim is to James).
In chapter 1:5, Paul mentions that the Thessalonian Christians were suffering for their faith. Their suffering had begun with persecution by the local Jewish community, mentioned in Acts 17, and Paul makes the point that they should view their trials as an evidence that they were being faithful to God! (His implication is that they would not be persecuted if they were not “standing up” for the gospel.)
Paul describes the judgement of those who persecuted them (along with those who “do not know God and…and do not obey the gospel…” – vv. 6-10) as God’s “repayment” for afflicting His people. This is one of the most vivid biblical descriptions of the judgement day, and when we couple it with what Paul previously wrote in 1 Thessalonians 4:13-17 and 5:2-3, it provides a very clear image of what THE “last day” will look like!
It is also important to note that two distinct groups of people are here singled out for condemnation: Those who are ignorant of God’s will, and those disobedient to it. It will not be enough – at the judgement – to plead, “I didn’t know” what the Lord expected; the information has been readily available to all who want to find it for almost two millennia, and continues to be today!
In chapter two we see that some of the Thessalonian saints were (apparently) still struggling with the notion that those who had already died had somehow “missed” the Lord’s return (vv. 1-2). Via inspiration, Paul reveals here that apostasy would occur among some of the saints before the time of that event would arrive (vv. 3-4). His statement, that “I told you when I was with you” (vs. 5) shows that this was not a “new” revelation, and Paul goes on to emphasize in verses 6-12 that, by “restraining” such opposition to Him at that moment in time, God was essentially “shaking out the dead wood” from the church.
Much has been made through the centuries of the identity of the “man of sin” or “son of perdition” mentioned in verse 3: Suggestions for the identity of this figure have ranged from Nero Caesar and various Roman Catholic popes to Adolph Hitler and Ronald Reagan! In the current generation, denominational authors Tim LaHaye, Jerry Jenkins, and John Hagee have again popularized the idea that this biblical figure will find a literal embodiment in the form of some world-dominating political personage. Such fanciful writers assert that this person will outlaw Christianity, demand that all people “worship” him, and somehow attempt to “overthrow” God. What we need to understand and remember, is that the apostle’s words must have an application to Christians in every generation – not merely to those of a particular moment in time. Therefore, what he is describing is a figure or an image, rather than a single person (“son of perdition” is simply a Hebrew idiom for a notably wicked person). The point in these verses is that God will allow those who are determined to resist or desert Him to experience the consequences of that choice (vv. 11-12). The description here (in chapter 2:3-4 and 2:7-10) forms a contrast to highlight the faithfulness of the Thessalonian Christians, which Paul praises in 2:13-15.