He shows us there that a soldier's primary responsibility is to please the one who enlisted him in this service. He makes it very clear that our primary responsibility, our loyalty is to Jesus Christ—not a corporation, not even to an apostle of that corporation. Christ is the one who enlisted us. The man was merely used.
He goes on to say that a soldier must be single-minded. If he is not single-minded, and gets himself involved in things other than carrying out the commands of his master, then that soldier is not going to be trustworthy. He is not going to be willing to endure hardship and put up with his share of suffering. He will not endure if he is deeply entangled in civilian pursuits, or distracted by other concerns.