Summary: God is not directing the defenses of nations today.
Usually, the kings of the cities would conscript people to erect fortifications and walls. 1Kings 9:15 (NIV), “Here is the account of the forced labor King Solomon conscripted to build the LORD's temple, his own palace, the terraces, the wall of Jerusalem…” The Lord supported the building of this type of defense for His nation, Israel.
When God made the Law Covenant with Israel, He had promised to protect His people – if they obeyed Him. Leviticus 26:3-6 (NKJV), “If you walk in My statutes and keep My commandments, and perform them, then…you shall…dwell in your land safely. I will give peace in the land, and you shall lie down, and none will make you afraid; I will rid the land of evil beasts, and the sword will not go through your land.”
Today, individual Christians also have God’s protection. Luke 4:10 (NLT), “For the Scriptures say, ‘He will order his angels to protect and guard you.’” Hebrew 13:6 (KJV), “we may boldly say, The Lord is my helper, and I will not fear what man shall do unto me.” We do not need to fear. 2 Timothy 1:7 (NKJV), "For God has not given us a spirit of fear, but of power and of love and of a sound mind."
Is God also managing the affairs of today’s nations? Because God has not made covenants with the earth’s nations, He is not directing their governments. The Apostle Paul calls the current world order “the present evil world,” (Galatians 1:4), and Satan the usurping prince (Ephesians 2:2). After Armageddon, God will help all peoples. Then Christ will establish His reign of peace on our wonderful earth. (Isaiah 35.)
Zechariah 14:2-3, 9 (NKJV), “For I will gather all the nations to battle against Jerusalem; The city shall be taken…Then the LORD will go forth And fight against those nations…And the LORD shall be King over all the earth.” Then “nation shall not lift up sword against nation, Neither shall they learn war any more. But everyone shall sit under his vine and under his fig tree, And no one shall make them afraid; For the mouth of the LORD of hosts has spoken,” Micah 4:3-4.
For a more detailed study, please see the free PDF, "What is This World Coming To?"