When Paul started the church at Thessalonica he was opposed by the Jewish community as well as the secular authorities (Acts 17:1-8). The Jews were reacting to Paul’s message that Jesus fulfilled the Old Testament prophecies, and the Roman city of Thessalonica reacted against Paul’s rejection of Caesar as Lord. As a result, he was forced to leave the city before he had fully prepared the church, and certainly before he wanted to leave.
It has only been a short time since he has been gone, but he things of the church often. The introduction to the book indicates that Paul prayed for the church each day, here he says that he thinks of the church often. Even though Paul’s desire was to return it is possible his enemies were slandering him by saying he never intended to revisit the church. Paul had taken all he could from the church and left them on their own to face a persecution Paul caused!
Paul says that he had a strong desire to return. The word for this desire is one of the strongest words for desire available to Paul, it means to “crave” something, usually in an especially inordinate way. In other places the word ἐπιθυμία is translated “lust.” This strong desire makes him make an effort to return. The verb σπουδάζω is not a light or a token effort, but rather doing “something with intense effort and motivation. Elsewhere the word is translated as “be eager to….” (Gal 2:10, Eph 4:3).
He made every effort to return, but Satan stopped him. The word“hinder” (ἐγκόπτω) has the sense of“tearing up the road.” If an army wanted to hinder another army from pursuing them they would tear up the road, burn the bridges, etc. Paul sees Satan’s operation as making any progress Paul might make very difficult. We are not told in Acts what Satan did to hinder him, it is possible that this was the threat of further persecution at the hands of the Jews and civil authorities in Thessalonica. On the other hand, Paul does not usually avoid ministry because of the threat of persecution.
This hindrance may have been more subtle, Paul’s efforts to travel back to the city were slowed by what might have seemed coincidental problems (travel plans fell through, etc.) The important thing to see here is that the source of Paul inability to return is Satan. The church is not suffering because of the civil authorities in Thessalonica, nor are they suffering because of jealousy from the synagogue, they suffer because they are engaged in spiritual warfare. As he says in Ephesians 6:10, the struggle is not against flesh and blood, but against the spiritual powers of darkness.