When we first read Luke 21:8, we have to wonder if the Apostles, who knew Jesus personally, could actually be deceived into believing another man was the Messiah. While I don’t believe the Apostles could have been deceived that another person was Jesus, I think, if they weren’t very cautious to consider Jesus’ words carefully, they could have been deceived into believing Jesus’ return to judge Jerusalem would be sooner than it was, and they could have left Judea prematurely without a witness. The text says that many would come in the name of Jesus and declare the time was at hand (Luke 21:8), i.e. the time of the end, or the time of the destruction of Jerusalem and the Temple was at hand. Jesus told the Apostles not to believe such people.
Notice that Jesus claimed the disciples would hear about wars (G4171) and commotions (G181), but these things didn’t foretell the end was near (Luke 21:9). The Greek words can be translated fights or battles (G4171) and disturbances or confusion (G181). Josephus records many such instances of the shedding of blood between Jews and gentiles and even Jews rising up against Jews in and around Judea and Galilee. So, states of disorder would exist at various times before the Jews’ war with Rome, but these things did not predict the coming of that final war that would judge the nation for rejecting their God and Savior.
Jesus told the Apostles that there would be wars and famines, pestilence, earthquakes, fearful sights and even signs from heaven (Luke 21:10-11). However, as mentioned in Luke 21:9, these kinds of things do not foretell the nearness of the end of the age. These kinds of things occur all the time. They occurred before the birth of Jesus, and they continued to occur throughout the 2000 years since Jesus was crucified.
The signs from heaven are matters of interpretation. In our modern day, we would look for great astronomical signs, perhaps a blood moon or a super nova or a planet pushed out of its course and colliding with another etc. Yet, it the first century AD the ‘heavenly signs’ were more likely to be astrological signs, like the Magi considered and came to find Jesus in Jerusalem, because Jupiter and Venus made a rare conjunction with the ‘king’s star’ Regulus in the constellation of Leo (the royal constellation and the sign representing the tribe of Judah).
Moreover, the position of the sun and the moon in the sign of Virgo (the sign of the virgin) as seen in Revelation 12:1 would be another example of a heavenly sign, pointing to the time of Jesus’ birth. Nevertheless, the ‘great signs from heaven’ in the context of Jesus’ words would be false signs from heaven. That is, the astrological signs would be interpreted mistakenly by folks (perhaps false brethren) saying the time is near (Luke 21:9).
The fact is that even before these things would occur, Jesus’ disciples would be betrayed and persecuted. Some would even be killed (Luke 21:12, 16; cf. Acts 12:1-2). Persecution would come in the form of arrests, spying upon the brethren,  beating them in the synagogues, and bringing them before rulers for trial etc. (Luke 21:12; cf. 2Corinthians 11:23-28). Nevertheless, all this would end up as a testimony, not only of the disciples’ own innocence and integrity, but also of the truth of the Gospel (Luke 21:13). This doesn’t necessarily mean the Gospel would be believed, but nothing evil could be legitimately said against it.
When such times occur, Jesus told his disciples not to think about what they would say to the authorities who commanded their arrest, because he, i.e. Jesus, would give them both a mouth and wisdom to reply so that their enemies would be unable to speak against or resist what they said (Luke 21:14-15).
 NOTE: the word persecute (G1377) is used by Paul to say he followed after (G1377) the knowledge and power of Christ’s resurrection and fellowship in his sufferings in an effort to lay hold of them (Philippians 3:10-12). Moreover, he advised others to follow after things like love, peace, kindness toward others etc. (Romans 14:19; 1Corinthains 14:1; 1Timothy 6:11; 2Timothy 2:22). The type of persecution Jesus spoke of seems to be the ‘obsession’ the enemies of the Gospel would have with believers, following them and spying upon them in an effort to do them harm.