"In the first tribulation do you believe there will be a 42 month period when the first beast (political/religious) will exist, and then Satan will come on the scene for the last 42 months, which has actually been shortened to a 5 month period?", (Question from Dewayne Short).
I believe that there will first be a league of nations, that will become the first beast with the arrival of the "little horn" of Daniel 7. The "little horn" will be a political leader who will be born of woman, and his rise to power will trigger the start of the 7 year tribulation period. However, his goal of a one world government will be resisted and initially fail. This initial defeat of the one world government is the deadly wound described in Revelation.
Then Satan will arrive on the scene at 42 months (3.5 years) in, and "resurrect" this one world government (see Revelation 13). He will ultimately succeed at establishing it, because he is supernatural and God will allow him to deceive the nations, uniting them all under the mark and system of the beast. The arrival of Satan at 42 months in will begin the great deception, during which the true Christians are going to have to flee to the hills, and wait for Jesus' return.
The second half of the tribulation period has not been shortened in terms of its length, but will be a full 42 months. The shortening of this period refers to when Jesus says, "And except that the Lord had shortened those days, no flesh should be saved: but for the elect's sake, whom he hath chosen, he hath shortened the days" (Mark 13.20 KJV bible). This "shortening of the days", refers to the supernatural ending of the great deception by Christ's physical return at 42 months into the 2nd period. So the entire tribulation will be a full seven year period, divided in half, and brought to a close by the return of Jesus Christ.