God used his warrior attributes to defend Israel.
True....but the whole reason David was honoured by God in the first place was because he was a faithful *pastor* (look up the link, even in the OT, between the two senses of that word)
Also, we're not OT Israel. We're not a theocratic nation who needs things like armies and whatnot. God's churches do not need warriors in the carnal sense, but in the spiritual (II Cor. 10:4).