'Imperial' in the Bible

Then the governor's soldiers took Jesus into the imperial headquarters and gathered the whole company of soldiers around him.

After reading the letter, he asked which province Paul was from, and when he learned that he was from Cilicia [an imperial province],

When it was decided that we were to sail to Italy, they handed over Paul and some other prisoners to a centurion named Julius, of the Imperial Regiment.

so that it has become known throughout the whole imperial guard, and to everyone else, that my imprisonment is in the cause of Christ.