There are many questions in Christian circles about the doctrine of the church being removed from the world prior to the Tribulation (Rapture). I would like to examine 1 and 11 Thessalonians and address some of the questions.
1Thes.4: But I would not have you to be ignorant, brethren, concerning them which are asleep, that ye sorrow not, even as others which have no hope.
 For if we believe that Jesus died and rose again, even so them also which sleep in Jesus will God bring with him.
 For this we say unto you by the word of the Lord, that we which are alive and remain unto the coming of the Lord shall not prevent them which are asleep.
 For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first:
 Then we which are alive and remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord.
 Wherefore comfort one another with these words.
In first Thessalonians the Apostle Paul wrote of the rapture to the church as well as at some point taught them in person (11 Thes. 2:5). From the tone and admonition in second Thessalonians it seems some false teacher(s) attempted to convince the saints they had missed the Rapture and were now in the Tribulation
And were now awaiting the Day of Christ. (In passing let me mention there are more than one Day of the Lord Luke 17:22)
2Thes.1: So that we ourselves glory in you in the churches of God for your patience and faith in all your persecutions and tribulations that ye endure:
 Which is a manifest token of the righteous judgment of God, that ye may be counted worthy of the kingdom of God, for which ye also suffer:
 Seeing it is a righteous thing with God to recompense tribulation to them that trouble you;
The church was indeed suffering tribulation by those who rejected the gospel but God is going to give payback to those people who persecute the body of Christ with a tribulation of their own.
 And to you who are troubled rest with us, when the Lord Jesus shall be revealed from heaven with his mighty angels,
 In flaming fire taking vengeance on them that know not God, and that obey not the gospel of our Lord Jesus Christ:
 Who shall be punished with everlasting destruction from the presence of the Lord, and from the glory of his power;
 When he shall come to be glorified in his saints, and to be admired in all them that believe (because our testimony among you was believed) in that day.
We, the Christians, will be at rest when Christ comes to wreck havoc on the lost. Not on the basis of our works but on the basis of our belief in the gospel.
 Wherefore also we pray always for you, that our God would count you worthy of this calling, and fulfil all the good pleasure of his goodness, and the work of faith with power:
 That the name of our Lord Jesus Christ may be glorified in you, and ye in him, according to the grace of our God and the Lord Jesus Christ.
We are not to be worried about the tribulation for ourselves but rather we should be walking a life that glorifies Jesus. The calling will be for us to be at rest while tribulation is pour out onto the lost.
2Thes.2: Now we beseech you, brethren, by the coming of our Lord Jesus Christ, and by our gathering together unto him,
 That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ is at hand.
 Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition;
We need not to worry about the day of Christ. The one where He is taking fiery vengeance on the lost because we will be gathered together with Him.
That Day, which day? THE DAY OF CHRIST WHERE IS TAKING FLAMING VENGEANCE ON THE LOST. All of these things must happen before the Day of flaming vengeance. So before the Day of Christ there must be a falling away first which is the precursor for the Rapture and the anti-Christ revealed.
Since we are still here (vs. 1) and the falling away has not happened (vs. 3) and the anti-Christ has not been revealed (vs. 3) the Day of Christ is NOT impending now.
All of the following must also occur before the day of flaming vengeance:
removal of the One who prevents it from happening now. (Holy Spirit)
the entering of the temple by the anti-Christ
the world following after him.
 Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God.
 Remember ye not, that, when I was yet with you, I told you these things?
 And now ye know what withholdeth that he might be revealed in his time.
 For the mystery of iniquity doth already work: only he who now letteth will let, until he be taken out of the way.
 And then shall that Wicked be revealed, whom the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming:
 Even him, whose coming is after the working of Satan with all power and signs and lying wonders,
 And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved.
 And for this cause God shall send them strong delusion, that they should believe a lie:
 That they all might be damned who believed not the truth, but had pleasure in unrighteousness.
 But we are bound to give thanks alway to God for you, brethren beloved of the Lord, because God hath from the beginning chosen you to salvation through sanctification of the Spirit and belief of the truth:
 Whereunto he called you by our gospel, to the obtaining of the glory of our Lord Jesus Christ.
 Therefore, brethren, stand fast, and hold the traditions which ye have been taught, whether by word, or our epistle.
 Now our Lord Jesus Christ himself, and God, even our Father, which hath loved us, and hath given us everlasting consolation and good hope through grace,
 Comfort your hearts, and stablish you in every good word and work.
We need not worry because we are called to salvation. Not only salvation from our sin but from the wrath to come. (1 Thes 5:9-10)
The comfort we have according to 1 Thes. 4 is the gathering out of the saints.