What does it mean to be a Soldier of Christ?

Soldier of Christ means those that preach the teachings of Christ; that's all. Jesus Christ was completely against fighting, killing or force. For example, the crusaders were a bunch of thieves that decided to kill and rob people that didn't accept Christianity, all the while they were sinning in the eyes of the same Christ they were fighting for. (But I always felt that they did what they did for power and money only, Christianity was used as an excuse to raid, rob and kill the non-believers)