http://www.youtube.com/watch?v=Zutuh0YCOqs
I actually fully agree with your before mentioned post, but I think it pertains to Apostles and disciples with a proselytizing-only mission (not for US Marines).
Jesus won the Crown of Martyrdom with obedience to God before all other lesser creatures. And by sacrificing His life, Jesus robs Satan of souls. Humans can achieve a similar victory of martyrdom.
******BUT FOR THE RECORD: The martyr I speak of is where one is murdered for his beliefs, not one who murders for his beliefs and is subsequently killed (or murdered by his own hand) because of his violent actions.
A US Marine’s mission is to an earthly country, but his soul still requires Salvation. The American government and all taxpaying voters don't have the ability to remove sin from the Marine’s soul. Thus, the Marine can give obedience to both country, and look for opportunities to tell others of Jesus Christ's love.
If there's a conflict between rendering unto a Cesar or that which must serve God, God comes first. Many a US military man and woman have the moral courage to reject false oaths for the Truth.
I seriesly think that if the US government tries to take away opportunities for obedience to God, then there won't be many volunteering for any military service, much less the Marine Corps. Those who would volunteer are not the type we'd want to have with military power.
I differ with your thought that Jesus' admonition to "be shrewd as serpents, and innocent as doves" is of limited scope in its application, but here's why:
Jesus is giving instructions to his Twelve Disciples starting from Matthew 10:5 all the way down through v.23, but as he gets to v.21 it becomes apparent that he's not just speaking about them right then and there, but about the entire future of Christianity right up to The Day of The LORD, because he says this:
21 "Brother will betray brother to death, and a father his child; and children will rise up against parents and cause them to be put to death. 22 "You will be hated by all because of My name, but it is the one who has endured to the end who will be saved. 23 "But whenever they persecute you in one city, flee to the next; for truly I say to you, you will not finish going through the cities of Israel until the Son of Man comes.
-- Matthew 10:21-23
All of that describes conditions that Christianity has understood to be future for over 2000 years, and from that reference to the future, right through the end of the chapter at v.42, Jesus continues with teaching that we unflinchingly embrace as being applicable to us, in this present day, and the transition to that teaching from his initial instructions is done in such a manner that we now have something of a quandry on our hands if we choose to assert that some portion of what he said is only applicable to those he was sending out at that time. It isn't clear where we should -- or even reasonably could -- draw a bright line in the text and say, "This part up to here applies to just the Twelve Disciples, and all of this afterward is what's applicable to all of us, too." Maybe after v.6?? Certainly before verse 15, though, and the part about serpents and doves is after that; in verse 16.
Another reason I think we can legitimately apply v.16 to "the now", is that we still ARE "sheep among wolves". That may be more apparent to believers in Communist China than to us at the local grocery store, but it is true, nonetheless, and since it is true, then it is simply a matter of logic to appropriate Jesus' ensuing admonitions for ourselves. If we are "sheep among wolves", then we should also "be shrewd as serpents, and innocent as doves."
There's also a good kernel of Truth at the heart of your thought about rejecting false oaths; that is, oaths to things that aren't true, or aren't based in truth. I want to see if I can expand on that to describe what I think is a godly approach.
When a Christian makes an oath, as when someone joins the Marines, I think God understands that oath to be a commitment to uphold all that does NOT conflict with what He has said, and I think that's how a Christian ought to understand it, as well. Does the fresh recruit know every standing protocol that is in effect?? No. So it stands to reason that there may come a moment when, despite his oath of service, the Christian Marine becomes aware of a conflict between what God has said, and what he has sworn to uphold. At such a time, it should be obvious that what God has said takes precedence, but it should ALSO be obvious that the conflict between God's Word and military protocol may not give the Marine license to entirely disregard the protocol. Certainly, as in the case of so many Christian martyrs, there are times where no avenue of compromise exists; where the conflict between the will of man and the word of God is so basic that the choice to obey man or God is strictly either/or. But where there is a way to achieve some kind of both/and solution; where God's word can remain uncompromised, and man's will can, at the same time, be least offended; then I think Paul's teaching about obedience to Earthly authorities puts us on solid ground, and we can legitimately appropriate Paul's admonition to "be in subjection, not only because of wrath, but also for conscience' sake" (cf. Romans 13:5). Where there is such a conflict, I think the Christian enlisted man has a duty before God, to do some more intensive homework and figure out how to obey God in a way that LEAST transgresses the stated protocol. In other words, to find the most harmonious accord between what God has said, "Do", and what the Marine Corps. has said, "Do not do."
So, making practical application to the specific case at hand, a wiser approach might be one that left no physical evidence, or it might require directing the spiritually curious to contact local Christian leaders who could carry the work of the gospel forward on a private, individual basis. It would require greater planning to carry that out, and it would require more prolonged, personal conversation with individual Iraqis, but it could be done. And, in truth, I think the more personal methods are better methods of evangelism, anyway. People who get tracts thrust at them, or coins slipped into their hands are liable to feel more like targets of a drive-by preaching than objects of the unimaginable love of an Almighty Creator, our Bridegroom God.
If we would win souls in Iraq, our foremost objective in evangelism MUST be to reveal to them that they are in that latter category, and not treat them like they are in the former.