The Hebrew term for “fortification” has the basic sense of a place that is impenetrable, inaccessible. (Compare Zec 11:2, ftn.) Fortifications of a town were costly and difficult and required an adequate defense force, so not all towns were fortified. The larger cities were usually walled cities; the smaller towns in that area, known as dependent towns, were unwalled. (Jos 15:45, 47; 17:11) Inhabitants of these towns could flee to the walled city in the event of an invasion by the enemy. Fortified cities thus served as a refuge for the people in the area. Cities were also fortified when they were strategically located to protect highways, water sources, routes to supply bases, and communication lines.

The strength and height of the fortifications of many cities in the Promised Land were such that the unfaithful spies sent by Moses to spy out Canaan reported that “the fortified cities are very great” and “fortified to the heavens.” From their faithless viewpoint the cities looked impregnable.​—Nu 13:28; De 1:28.

Cities in Bible lands generally covered an area of but a few acres. Some, however, were much larger. The capital cities of Egypt, Assyria, Babylonia, Persia, and Rome were exceptionally large. Babylon was one of the most strongly defended cities in Bible times. Not only did it have unusually strong walls but it was situated on a river that provided a fine moat for defense as well as a water supply. Babylon felt she could hold her captives forever. (Isa 14:16, 17) But the city was taken in one night by the strategy of Cyrus the Persian, who diverted the Euphrates so that his forces could enter the city through gates in the walls along the quays.​—Da 5:30.

Three essentials were required for a fortified city: (1) walls to act as a barrier to the enemy, (2) weapons so that the defending forces could retaliate to repel the attackers, and (3) an adequate water supply. Foodstuffs could be stored during times of peace; but a constant, accessible source of water was essential for a city to withstand a siege of any length.

Moats and Ramparts. Some cities were surrounded by a moat filled with water, especially if a river or lake was nearby. Babylon on the Euphrates was a notable example, as was also No-amon (Thebes) on the Nile canals. (Na 3:8) Where there were no nearby bodies of water, a dry moat was often constructed. Jerusalem was rebuilt with a moat.​—Da 9:25.

Rising from the side of the moat was a “rampart” built from the earth dug up when the moat was excavated. (2Sa 20:15) This rampart sometimes was covered with a stone facing and formed a glacis, or incline, sloping up to the wall built on top of the rampart. The moat discovered by archaeologists on the western defenses of the  city of Hazor was 80 m (262 ft) wide at the top, 40 m (131 ft) across the bottom, and about 15 m (50 ft) deep. The rampart rising from the moat was an additional 15 m (50 ft). This made the top of the rampart nearly 30 m (100 ft) high, measuring from the bottom of the moat. On top of this stood the city wall.​—Compare Ps 122:7.

This rampart was, of course, very difficult to ascend, especially with battering rams, for which reason the attackers built a ramp, or “siege rampart,” up which the battering rams were moved. (2Sa 20:15; see BATTERING RAM.) The moat was so wide that it greatly weakened the archery fire of the attacking army, and shooting from the bottom of the moat accomplished little. On the other hand, the builders of the ramps for their battering rams were under constant fire from the city walls, being subjected to a rain of arrows, stones, and sometimes firebrands. Of course, not all cities had moats or sloping ramparts, some basing their defense entirely on vertical walls.

The Walls. After the moat and rampart, the wall was the next feature of the defenses. Some walls and towers provided fortified positions for soldiers and rooms for storage as well as ladders to the top. The wall was made up of large stones, brick, and earth. Some of the stones were enormous in size. Earlier walls were mostly made of stones without mortar. Later on, mortar was often used between the stones. Mortar was made by treading clay with the feet and mixing it with water, as in making bricks. Otherwise it would crack and weaken the defensive wall.​—Compare Eze 13:9-16; Na 3:14.

The wall system often consisted of a high inner wall and a lower outer wall. A dry moat was sometimes constructed between these walls. Along the outer wall were bastions, round or square in shape. They were crenellated (indented with battlements) so that the archers could shoot through the embrasures and at the same time receive some protection against enemy arrows and rock slingers. Bastions extended out from the wall so that the archers not only could command the area in front of them but could also shoot to the right or to the left at the flanks of the enemy forces that might be trying to scale or breach the wall.

The inner wall was heavier and thicker. After the invention of the heavy battering rams, especially like those used by the Assyrians, much stronger, thicker walls were built to withstand the devastations of this instrument. A stone wall at Tell en-Nasbeh (Mizpah?) was found to average 4 m (13 ft) in thickness, and it is estimated to have been 12 m (39 ft) high. The top of the wall was crenellated, as were nearly all city walls.

Towers and Gates. Towers were built into the inner walls (in addition to bastions or towers in the outer walls). They were higher than the wall, protruding from the wall sometimes as much as 3 m (10 ft). They were equipped with crenellations on top and sometimes with openings below the crenellations, for the convenience of archers and stone throwers. The fact that the towers protruded from the wall and were never placed farther than two bowshots apart, but were usually much closer, enabled the defenders to command all the area along the wall. Also, a balcony at the tower’s top had openings in the floor so that archery fire, stones, and firebrands could be directed straight down at the invaders below. These towers are mentioned many times in the Scriptures. (Ne 3:1; Jer 31:38; Zec 14:10) Towers served also as posts for watchmen, who could see the enemy approaching from a distance.​—Isa 21:8, 9.

Usually the citadel was built on the highest elevation in the city. It had a tower fortress and its own walls, less massive than the walls surrounding the city. The citadel was the last stronghold of refuge and resistance. When the soldiers of the enemy breached the city walls, they would have to fight through the streets of the city to reach the tower. Such a tower was the one at Thebez, which Abimelech attacked after capturing the city and where a woman broke his skull by pitching an upper millstone upon his head.​—Jg 9:50-54.

Besides these city towers, other towers (Heb., migh·dalʹ; plural, migh·da·limʹ) were built in isolated places. These were constructed as “police stations” to protect wells or other water sources, highways, frontiers, communication lines, or supply lines. King Uzziah of Judah is noted for building towers in Jerusalem as well as in the wilderness; these apparently were erected to protect the cisterns that he built for watering his livestock. (2Ch 26:9, 10) Several of such towers have been found in the Negeb.

The weakest part of the defenses of a city were its gates; therefore the gates were the most hotly defended points in the walls. Only as many gates were constructed as necessary for the traffic of the inhabitants in and out of the city during peacetime. Gates were made of wood or of wood and metal, sometimes being metal covered to resist fire. In archaeological diggings the  gateways are often found to be charred, indicating that fire was used in an attempt to burn the gates down.​—See GATE, GATEWAY.

Some of the kings of Judah noted for their construction of fortifications were Solomon, who built “fortified cities with walls, doors and bar”; Asa, who put up cities with “walls around and towers, double doors and bars”; and Uzziah, who built “towers in the wilderness” and “engines of war” in Jerusalem.​—2Ch 8:3-5; 14:2, 6, 7; 26:9-15.

Fortifications of the Besieging Army. At times the besieging army built fortifications of its own around its camp. This protected the camp from sorties on the part of those besieged or from attacks by outside allies of the city. These fortified camps might be round or oval in shape and surrounded by a wall, which was often crenellated and had crenellated towers. For these fortifications, they would cut down the trees, sometimes for miles around the city. Jehovah’s law directed the Israelites not to cut down fruit trees for this purpose.​—De 20:19, 20.

Fortifications With Pointed Stakes. When foretelling the destruction of Jerusalem, Jesus Christ indicated that her enemies would build around her “a fortification with pointed stakes,” or, “palisade.” (Lu 19:43, Int) The historian Josephus confirms the accurate fulfillment of this prophecy. Titus argued in favor of building a fortification to keep the Jews from leaving the city, in order to bring about their surrender or, if this did not materialize, to make it easier to take the city because of the resultant famine. His arguments won out, and the army was organized to undertake the project. The legions and lesser divisions of the army competed with one another to finish the task; individually the men were spurred on by a desire to please their superiors. To provide materials for the construction of this fortification, the countryside about Jerusalem within a distance of about 16 km (10 mi) was denuded of its trees. Amazingly, according to Josephus, the over 7-km-long (4.5 mi) fortification was completed in just three days, an undertaking that ordinarily would have required a number of months. Outside the wall of this fortification, 13 places for garrisons were constructed, and their combined circumference amounted to about 2 km (1 mi).​—The Jewish War, V, 491-511, 523 (xii, 1, 2, 4).

Archaeological Discoveries. Following up the building operations of his father David, King Solomon was outstanding for his construction works. Besides building the magnificent temple of Jehovah at Jerusalem, he strengthened Jerusalem’s walls and built extensive fortifications at Hazor, Megiddo, and Gezer. Archaeologists were guided in their excavation of these fortifications by the Bible’s statement at 1 Kings 9:15: “Now this is the account of those conscripted for forced labor that King Solomon levied to build the house of Jehovah and his own house and the Mound and the wall of Jerusalem and Hazor and Megiddo and Gezer.” They found that the gates of these three last-named cities were all built to a single unique plan, each being 17 m (56 ft) wide, with an entrance flanked on both sides by square towers and leading into a vestibule 20 m (66 ft) long, with three chambers on each side. They were somewhat similar to the description of the gates of Ezekiel’s visionary temple.​—Eze 40:5-16.

Immediately above walls built by Solomon at Megiddo and Hazor, other walls were constructed, possibly by Ahab. These were more thickly and strongly built, doubtless because of the heavy Assyrian battering rams in use during that later period.

The source of water for Megiddo was a well in a natural cave at the western foot of the mound on which the city was built. To get water into the city, they sent a vertical shaft 30 m (98 ft) deep, 22 m (72 ft) of this distance through solid rock; this brought them to the level of the well. From this level they cut a horizontal tunnel with a slight gradient for a distance of 67 m (220 ft) to the well. The slight slope from the well to the bottom of the shaft allowed the water to flow into the city by gravity. The well was sealed from the outside by a thick wall.

Even greater engineering skill was required when Hezekiah sealed up the course of the water flowing from Gihon and cut a channel of some 533 m (1,749 ft) to bring water into Jerusalem, thereby enabling the city to withstand a long siege.​—2Ch 32:30.

Often cisterns, both public and individual, were built inside a city to supply the city with water during times of siege. On the monument (now located in the Louvre of Paris) erected at Dibon, in Moab, by Mesha the king of Moab, we find the inscription: “I also built its gates and I built its towers and I built the king’s house, and I made both of its reservoirs for water inside the town. And there was no cistern inside the town even at the acropolis, so I said to all the people, ‘Let each of you make a cistern for himself in his house.’”

Symbolic Uses. Since the towers in the wilderness were the safest places of refuge for miles  around, we can see the appropriateness of Proverbs 18:10: “The name of Jehovah is a strong tower. Into it the righteous runs and is given protection.” Also significant are the expressions in Psalm 48: “In [Zion’s] dwelling towers God himself has become known as a secure height. March around Zion, you people, and go about it, count its towers. Set your hearts upon its rampart. Inspect its dwelling towers, in order that you may recount it to the future generation.” (Compare Heb 12:22.) This would be especially meaningful to Jews who would look up at the great stronghold of Jerusalem situated on an elevation higher than nearly any other major capital city in human history, with its mighty walls of defense. Through the prophet Zechariah, Jehovah speaks of himself as “a wall of fire all around” Jerusalem. This gives his people encouraging assurance that, while walls of stone can be broken down, Jehovah himself is really the defense of his servants.​—Ps 48:3, 11-13; Zec 2:4, 5.