I would imagine that a Roman centurion that was a part of the Imperial Regiment would be used to being in charge no matter what. Pretty much everyone that he came into contact with would have to obey him, and I'm sure that he was a fairly proud man. I would be. It was an honor enough to be a part of the Roman army, the finest fighting machine the world had ever seen, and to be a part of the Imperial Regiment was a cut above even that. He was one of the best at what he did and I'm sure that he was not used to taking orders from very many people. He spent most of his time giving orders.
Julius was just such a soldier, but he wasn't just a soldier. He was man. This chapter sheds some light on his humanity when he allows Paul to go and visit his friends in Sidon. Not only that, but it also tells us that he probably knows a little bit about why Paul is going to Rome. He's not treating Paul like an ordinary criminal because he realizes that Paul wants to make this journey, so there's little risk of him running away. Basically, we're dealing with a smart, relatively kind, proud man. So why does he have so much trouble with simple instructions?
Paul tries to tell them early on that things are going to get bad. We don't know for sure why Paul made that prediction. Perhaps it was from his travel experiences over the last several years, or perhaps it was a direct message from God. It really doesn't matter. His was a voice of wisdom that went unheeded. I imagine that Julius thought that there was no way that this intellectual could possibly know much about traveling the Mediterranean, so why listen to him? Paul was ignored and Julius moved ahead under the advice of the ship's captain.
When things started to get bad, it moved in slowly, and initially, Julius and the crew thought that they were being favored. The wind was picking up and things seemed to be going well. Looking back, of course, we ask, shouldn't an experienced sailor on the Med have thought about Paul's warning and realized that this south wind was a portent of disaster?
As predicted, things did get pretty bad in a hurry. A hurricane force storm blew up and trapped the ship. The men were wondering if they would survive, and Paul received a message directly from God. He told the men that they would be saved, but that the ship would be lost. They would have to run aground on an island somewhere in the sea, but they would survive and Paul would reach Rome.
Still some of the men did not believe that Paul knew what he was talking about and they tried to sneak off the ship in a life boat. Julius, though, was finally coming to understand the wisdom of Paul's words and he prevented their escape. When they finally did run aground, the other soldiers wanted to kill the prisoners to prevent them from escaping, but Julius had made it that last step and apparently realized that if God had promised their survival to Rome, then he would not allow the prisoners to escape either, so he spared their lives. Julius was finally understanding that there are things in this world that he could not and would not ever be able to control. No matter his position before men, God would always be in charge.
We don't know whether Julius ever became a Christian or not, but through this story, we see the importance of keeping our pride in check and not letting one bad decision escalate into a horrible situation.