"a good soldier" - The metaphor of the Christian life as warfare (against the evil world system, the believer's sinful human nature, and Satan) is a familiar one in the NT (cf. 2 Cor. 10:3-5; Eph. 6:10-20; 1 Thess. 4:8; 1 Tim. 1:18; 4:7; 6:12). Here Paul is dealing with the conflict against the hostile world and the persecution (cf. v. 9; 1:8; 3:11,12; 4:7).