A quote from the appendix to Guy Hershberger’s 1969 3rd edn of War, Peace and NonResistance, where he answers various practical objections.
13. Are Not Soliders in Need of the Gospel? Therefore Does Not Army Service, Especially Service as an Army Chaplain, Provide a Fine Opportunity to Testify for Christ?
It is true that the soldier needs the Gospel as much as any other man, and that the nonresistant Christian should not hesitate to bring it to him if he can do so without being part of the military organization. But to be a member of an organization whose task it is to kill would certainly disqualify one to preach the gospel of love and nonresistance. (p. 314)
I wish he had expanded on his answer at much greater length. But a nice start.