Meanwhile, Saul was still breathing out murderous threats against the Lord’s disciples. He went to the high priest 2 and asked him for letters to the synagogues in Damascus, so that if he found any there who belonged to the Way, whether men or women, he might take them as prisoners to Jerusalem. 3 As he neared Damascus on his journey, suddenly a light from heaven flashed around him. 4 He fell to the ground and heard a voice say to him, “Saul, Saul, why do you persecute me?”5 “Who are you, Lord?” Saul asked. “I am Jesus, whom you are persecuting,” he replied. 6 “Now get up and go into the city, and you will be told what you must do.”7 The men traveling with Saul stood there speechless; they heard the sound but did not see anyone. 8 Saul got up from the ground, but when he opened his eyes, he could see nothing. So, they led him by the hand into Damascus. 9 For three days he was blind and did not eat or drink anything. Acts 9:1-9
What are the greatest events in the History of the World? Viewing things through the Kingdom of Heaven mindset we would have to say the incarnation of Jesus where God invaded this planet as a human to save us. Secondly, Jesus death on the cross where He made a way for all mankind's sin to be forgiven and a relationship restored with our Maker. Third, the resurrection where death was defeated and God made a way to live forever with Him. And fourth, the sending of the Holy Spirit so we can be made spiritually alive with God living inside us. There are more to come but after those four not many events are much more significant than what happens here in Acts 9, the conversion of Saul. The gospel was spread completely throughout the known world because of his faithfulness. When we get to Heaven, Paul's family tree of believers is going to resemble Noah's family tree of humans. And where would we be without Romans, 1&2 Corinthians, Galatians, Ephesians, Philippians, Colossians, 1&2 Thessalonians, 1&2 Timothy, Titus, and Philemon and possibly Hebrews?
I am big into free will where a person is headed one way and repents of their sin being convicted by the Holy Spirit, and turns and chooses to follow Christ. Here is an instance where God invades and does the turning. God sees who He wants and knocks him off his donkey and sends him the other way. I still see it as free will though where Father God, not the Godfather, makes him an offer he can't refuse.
Why Saul? He was perfectly suited for the task. He had a zealous personality. Like a dog sniffing a scent, Paul's scent would be evangelizing Gentiles, and nothing could stop him. He also was multilingual being highly educated, which would serve him well as he crossed continents with the Gospel. He was a Roman Citizen which got him a "Get out of Jail Free card" in a few instances. He was an Old Testament scholar so once his wrong thinking got turned around as he sat in darkness for three days, he "saw" the scripture through the eyes of Jesus being the prophesied Messiah who would come two times; the first as a suffering savior and the second as a conquering triumphant king. This enabled him to preach while reasoning effectively from the scriptures and write epistles that effectively transitioned new believers from the old covenant to the new covenant.
You may not be a Saul but God has knocked you at some point off your donkey and headed you in a direction following Jesus for a unique calling that only you can perform. Are you zealously, faithfully performing it? Do you even know what "it" is? Paul said, "We are His workmanship whom God created to perform previously ordained for us, good works." God has given us gifts and abilities to perform these. Are you just sitting around in the dark or are you up and doing them?