In the Bible, warfare is a significant theme, particularly in the Old Testament, where the Israelites often engaged in battles as they settled in the Promised Land. The instructions for warfare provided in the Scriptures are not merely tactical but are deeply rooted in spiritual and moral principles. These instructions reflect God's sovereignty, justice, and holiness, and they emphasize the importance of faith, obedience, and righteousness.

Divine Command and Guidance

The Israelites were often commanded to go to war by direct instruction from God. In Deuteronomy 20, God provides specific guidelines for warfare, emphasizing reliance on Him rather than on military might. "When you go out to war against your enemies and see horses and chariots and an army larger than yours, do not be afraid of them, for the LORD your God, who brought you out of the land of Egypt, is with you" (Deuteronomy 20:1). This passage underscores the importance of trusting in God's presence and power rather than in human strength.

Priestly Encouragement and Exemptions

Before battle, a priest was to address the troops, reminding them of God's presence and encouraging them not to fear. "He shall say to them, 'Hear, O Israel, today you are going into battle against your enemies. Do not be fainthearted or afraid; do not be alarmed or terrified because of them. For the LORD your God goes with you to fight for you against your enemies, to give you victory'" (Deuteronomy 20:3-4). Additionally, certain individuals were exempt from military service, such as those who had built a new house, planted a vineyard, or were betrothed, as well as those who were fearful (Deuteronomy 20:5-8).

Offer of Peace and Rules of Engagement

The Israelites were instructed to offer terms of peace to a city before attacking it. If the city accepted, its people were to become forced laborers. If not, the city was to be besieged, and upon capture, the men were to be killed, but women, children, and livestock could be taken as plunder (Deuteronomy 20:10-15). However, for the cities of the nations that God was giving them as an inheritance, the Israelites were commanded to destroy them completely, to prevent the influence of idolatry (Deuteronomy 20:16-18).

Prohibition Against Destruction of Resources

In warfare, the Israelites were instructed not to destroy fruit-bearing trees, recognizing the importance of preserving resources for future generations. "When you lay siege to a city for a long time, fighting against it to capture it, do not destroy its trees by putting an ax to them, because you can eat their fruit. Do not cut them down. Are the trees of the field human, that they should be besieged by you?" (Deuteronomy 20:19).

Spiritual and Moral Conduct

The conduct of the Israelites in warfare was to reflect their covenant relationship with God. They were to maintain purity and holiness, even in the camp. "When you are encamped against your enemies, then you shall keep yourself from every evil thing" (Deuteronomy 23:9). This included maintaining cleanliness and addressing any moral or ritual impurity.

Reliance on God and Obedience

Throughout the biblical narrative, the success of Israel in warfare was contingent upon their obedience to God's commands and their reliance on Him. Disobedience and sin often led to defeat, as seen in the battle of Ai (Joshua 7). Conversely, when the Israelites followed God's instructions, they experienced miraculous victories, such as the fall of Jericho (Joshua 6).

These instructions for warfare highlight the unique relationship between God and His people, where military endeavors were not merely human efforts but acts of divine purpose and fulfillment of God's promises.