Tunnel warfare

Tunnel warfare is about using tunnels and underground spaces in battles. Soldiers build tunnels to hide, move secretly, or launch surprise attacks. They can also use natural caves for the same reasons. Tunnels help defend a place by allowing troops to ambush enemies or move around without being seen.

People have used tunnels in wars for a very long time. For example, defenders of strong forts would dig tunnels to try to break through enemy walls. Attackers would dig tunnels too, to get closer to the fort or to blow it up. In cities, tunnels are often used in fights between groups, like in the Syrian Civil War in Aleppo.

Being inside a tunnel is tricky because there is very little space. Soldiers can only see and shoot in a few directions at once. Tunnels can be like a maze with dead ends and dark areas, making battles inside them feel like fighting at night.

Pre-gunpowder

Antiquity

Ancient Greece

Historian Polybius wrote about old ways of fighting during sieges in his book Histories. He told how soldiers would dig tunnels to get close to enemy walls. In one story, Roman soldiers dug secret tunnels to get near the city of Ambracia. The people inside the city found the tunnels by listening for digging sounds and then dug their own tunnels to meet the Romans underground.

The people of Prinassos used tricks to make their town seem easier to attack. When soldiers from Macedon tried to dig tunnels, the town’s people made it look like the work was almost done, tricking the attackers into thinking they had already broken through.

Roman

The Romans also used tunnels and hidden paths to surprise enemies. After a big uprising, groups of people in Batavi used hidden trenches and tunnels to hide and attack Roman soldiers. Roman troops learned to be very careful when moving through areas that might have these hidden traps.

During a big fight called the Bar Kokhba revolt, Jewish fighters used tunnels to hide from Roman soldiers. The Romans found these tunnels and sometimes set fires to smoke out the people inside.

China

In very old China, soldiers also used tunnels during sieges. When enemies tried to dig under city walls, defenders would send smoke into the tunnels to chase them away.

Post-classical

During the Middle Ages, soldiers dug tunnels to weaken castle walls. They would dig under the walls and then fill the tunnels with things that burn. When lit, the supports in the tunnels would burn, and the walls would fall down.

Defenders had ways to stop this. They could build their castles on very hard ground or add deep ditches around them. They could also dig their own tunnels to attack the diggers or to collapse the attackers’ tunnels. If the walls were broken, they would put up barriers to slow down the attackers.

Coming of gunpowder

In the 15th century, a big change happened in tunnel warfare in Italy when people learned to use gunpowder. Gunpowder made it easier to break through walls and caused more damage.

One famous example was when Ivan the Terrible captured Kazan by using explosions to weaken its walls. Fortresses started building special tunnels called "hearing tunnels" to detect enemy digging from far away. The Kremlin had these kinds of tunnels too.

Later, during battles, soldiers began using tunnels called saps to get closer to enemy positions safely. Military leaders wrote books about the best ways to attack and defend using these tunnels.

19th century

Crimean War

In the mid-1800s, during the Siege of Sevastopol (1854–1855), soldiers on both sides dug many tunnels underground. The Russians dug more tunnels and used less gunpowder, while the other side used more gunpowder but had trouble with their tools. The tunnels were very hard to work in because of poor air and water.

American Civil War

See also: Battle of the Crater

In 1864, during the Siege of Petersburg, Union soldiers dug a tunnel and placed a large amount of gunpowder under the Confederate lines. When they exploded it, a big hole opened in the defenses of Petersburg, Virginia. However, the battle did not go well for the Union soldiers who tried to attack through the crater. The Confederate soldiers fought back successfully.

During the Siege of Vicksburg in 1863, Union troops also dug a tunnel and set off an explosion under Confederate trenches. Although they managed to get into the trenches, they were later forced to pull back.

Modern warfare

The increased firepower from using new explosives made building strong above-ground defenses very costly. As a result, defenses were built underground to offer more protection. These underground shelters had openings to fire weapons like artillery and machine guns.

During World War I, soldiers used tunnels as a strategy to break the stalemate of trench warfare. Miners dug tunnels under areas between enemy lines to place explosives, aiming to destroy enemy positions and create confusion. This tactic was used in battles like the Battle of the Somme and the Battle of Vimy Ridge. In some cases, miners from opposing sides would accidentally meet underground, leading to fights in the tunnels.

In the Chaco War, Paraguayan troops used a tunnel to attack Bolivian forces from behind and won the battle. During World War II, Chinese forces used tunnels to hide and attack Japanese troops, with hidden entrances in houses or wells. Similar tactics were used by Japanese forces in battles like Iwo Jima, where they built tunnels under Mount Suribachi.

In the Korean War, North Korean forces built extensive tunnel networks to protect themselves from air attacks and to launch surprise attacks. During the Vietnam War, Viet Cong forces used a vast tunnel system near Saigon to hide supplies and launch attacks. These tunnels included living spaces, hospitals, and workshops.

In more recent conflicts, groups like Hezbollah and Hamas have used tunnels for defense and attacks. During the Russian invasion of Ukraine, both Ukrainian and Russian forces used tunnels to protect themselves and launch surprise attacks on their enemies.