Acquiring offensive weapons is forbidden (Deut 17:16: Joshua 11:6). That rules out high-powered rifles, machine guns and artillery.
Participation in defence of the community is voluntary. No one should be forced to engage in fighting against their will. Compulsory military training and service is forbidden (Jud 7:3).
Men who have recently married, or built a house or started a business should not be involved in defence, because they need to focus their attention on what they have just started (Deut 20:5-7).
People who are afraid or tender-hearted should be freed from defensive activities (Deut 20:8).
God's people must not to form alliances with powerful nations (Is 31:1).
The people must defend themselves with what they have (1 Sam 13:22). They would use the tools and equipment that they already had for use on their farms and in their households. Knives and hayforks were their only weapons. This prevents them from relying on their weapons rather than on God.
The community must not waste resources making or buying weapons of war. In Samuel's time, the children of Israel did not have blacksmiths. They relied on the Philistines for sharpening their ploughshares, axes and sickles (1 Sam 13:21). From an economic perspective, this was unwise, but from the perspective of faith, it was perfect. None of the Israelites except Saul or Johnathan had a sword or spear (1 Sam 13:22). The Philistines had 3000 chariots with two skilled soldiers for each chariot (1 Sam 13:5). Israel was outnumbered in men and weapons, but that did not matter. I was perfect, because they had to rely on God for their physical protection.
All military leaders must be temporary. They are given authority by local communities when a threat arises, but they must go back to their normal lives when the battle is complete. This limits their ability to fight wars, but it is better than having permanent military leaders who become advocates for unnecessary wars.
Professional military forces are dangerous, because those who constantly train for war eventually start looking for opportunities to fight. Under God's model of defence, ordinary people come together to defend their communities. They will not be skilled fighters, but that does not matter, because they will be forced to rely on God.
These restrictions mean that ability of the people of God to engage in warfare will be very limited. This has the following benefits.
Military adventures to gain wealth by seizing control of another community are not practical.
Empire building is impossible.
Using miliatry power to advance democracy and capitalism would be impossible.
When a community faces an external military attack, they will usually have to sue for peace.
If they choose to resist the invader, they will have to rely on God's assistance. If God does not come to their aid, they will fail.
Jesus confirmed this principle when he faced a threat of attack by hostile forces. He checked to see if his disciples were armed. Only two of his disciples had swords.
The disciples said, "See, Lord, here are two swords." "That's enough!" he replied (Luke 22:38).The disciples had two swords. "Machaira" refers to a short sword or long knife that was better for defence than attack. It would have many uses in a Jewish household for cutting food and cloth, so it was not surprising that the disciples had a couple of them.
Jesus said that two knives were enough for a dozen men, even during a crisis when the authorities were and hostile their lives were under threat. With two knives, twelve men could protect themselves from a small gang of robbers, but nothing more. They would not be capable of dealing with a bigger threat.
When Jesus said that two swords would be enough, he was applying the principle articulated in God' law that his people should be weak in weapons, so they would rely on the power of God. Jesus understood the importance of spiritual power.
Do you think I cannot call on my Father, and he will at once put at my disposal more than twelve legions of angels (Matt 26:53)?Jesus did not need physical weapons, because he trusted his Father. However, his disciples would not have the same level of faith, so he was happy for them to have a couple of weapons in case they came under attack. But he wanted them to be weak, so they would be forced to trust in God.
Once Jesus was confronted by a "crowd armed with swords and clubs" sent by the Jewish authorities (Mark 14:23), Jesus counted the cost, and decided that he would surrender to them, even though they had no legal authority to arrest him. He chose to go to his death, rather engage in a futile fight.
That principle has not changed. Jesus still prefers that his people trust in him for their protection, rather than relying on weapons of war. War does such terrible harm, it is usually better to suffer and die, than to go to war.