Something to keep in mind is that the military at that time also followed
God's laws.
Even Abraham who found favor in Gods sight had his own army.
Genesis 14:14 "And when Abram heard that his brother was taken captive, he
armed his trained servants, born in his own house, three hundred and eighteen, and pursued them unto Dan."
Self Defense
Exodus 22:2 "If a thief be found breaking up, and be smitten
that he die, there shall no blood be shed for him."
Psalms 144:1 "Blessed be the LORD my strength which teacheth my hands to war, and my fingers to fight:"
Luke 22:35-38 "And he [Jesus] said unto them, When I sent
you without purse, and scrip, and shoes, lacked ye any thing? And they said,
Nothing. Then said he unto them, But now, he that hath a purse, let him take
it, and likewise his scrip: and he that hath no sword, let him sell his
garment, and buy one... And they said, Lord, behold, here are two
swords. And he said unto them, It is enough."
Did Jesus in this verse advocate the use of a sword for self-defense
purposes? Clearly if he was not, when they announced we have two swords Christ
would have clarified other wise.
For those that use the sixth of the Ten Commandments as their reasoning for
not fighting "Thou Shalt Not Kill" in fact, the correct translation of
this scripture is "Thou Shalt Not Murder" which has a whole different
meaning than the previous one. Murder is the unlawfully taking of a human life.
"St. Paul…approved of capital punishment—he says ‘the
magistrate bears the sword and should bear the sword.’ It is recorded that
the soldiers who came to St. John Baptist asking, ‘What shall we do?’
were not told to leave the army. When Our Lord Himself praised the Centurion
He never hinted that the military profession was in itself sinful. This has
been the general view of Christendom. Pacifism is a very recent and local
variation. We must of course respect and tolerate Pacifists, but I think
their view erroneous." —C.S. Lewis, Letters of C.S. Lewis, 1952
Military Service
Numbers 1:2-3 "Take ye the sum of all the congregation of the
children of Israel, after their families, by the house of their fathers,
with the number of their names, every male by their polls; From
twenty years old and upward, all that are able to go forth to war in
Israel: thou and Aaron shall number them by their armies."
Throughout the Old Testament, it is clear that men in Israel over the age of
20 were to fight in their wars. Usually the call (horn blown) would go out and
thousands of fighting men would be gathered to battle. The first standing armies
where created under King Saul.
Deuteronomy20:5-8 "And the officers shall speak unto the people,
saying, What man is there that hath built a new house, and hath not
dedicated it? let him go and return to his house, lest he die in the battle,
and another man dedicate it. And what man is he that hath planted a
vineyard, and hath not yet eaten of it? let him also go and return unto his
house, lest he die in the battle, and another man eat of it. And what man is
there that hath betrothed a wife, and hath not taken her? let him go and
return unto his house, lest he die in the battle, and another man take her.
And the officers shall speak further unto the people, and they shall say,
What man is there that is fearful and fainthearted? let him go and return
unto his house, lest his brethren's heart faint as well as his heart."
Deuteronomy 24:5 "When a man hath taken a new wife, he shall not
go out to war, neither shall he be charged with any business: but he shall
be free at home one year, and shall cheer up his wife which he hath
taken."
Military service was not mandatory, under certain circumstances one could
defer service, and those that where "fainthearted" could avoid it all
together.
Proverbs 20:18 "Every purpose is established by counsel: and with
good advice make war."
It should be noted, that in the old testament it was usually the Lord who
declared who to attack when entering the promised land and not the leaders.
Fighting in self defense [an unprovoked attack] of ones country would
always be the right thing to do, but clearly one could take that too far.
John 18:36 "My kingdom is not of this world. If My kingdom were
of this world, then My servants would be fighting, that I might not
be delivered up to the Jews; but as it is, My kingdom is not of this
realm"