Remember that there are two phases of the coming of Christ. First, He will come into the air and call out His saints to meet Him. This is the first part of His coming, the part always referred to by Jesus when He said, "Watch, therefore, for ye know neither the day nor the hour wherein the Son of man cometh" and made similar statements. Then on the earth there will intervene the seventieth or last "week" of Daniel's prophecy (Dan. 9:24-27). On the earth then there will be "the beginning of sorrows," and in the last half of the "week," three and one half years of great tribulation while the Antichrist rules the world. Then Christ will return from Heaven, coming literally in the clouds with the saints and angels to fight the battle of Armageddon, destroy the kingdoms of the Antichrist, and reign upon earth. During the great tribulation this gospel of the kingdom will be preached to all the world and then will come the end of the tribulation in the battle of Armageddon when Christ comes to set up His kingdom. That is what Matthew 24:14 means. The gospel or good news of the coming reign of Christ will be preached by a newly converted remnant in all the world after Christ comes and takes away His saints.