Tunnel warfare
This tunnel network proved its use in the Battle of Triangle Hill in October and November 1952, where, despite the United States Eight Army enjoying complete air and artillery superiority, the Chinese managed to keep the hill and inflict heavy casualties on the Americans.

Vietnam War: To maintain a full-scale guerrilla war in South Vietnam, camouflaged bases were used capable of supplying the guerillas for a long period of time. Throughout South Vietnam, there were secret underground bases that operated successfully. There are reports that every villager was obliged to dig 90 cm (35 in) of tunnel a day. The largest underground base was the tunnels of Cu Chi with an overall length of 320 km (200 mi). To combat the guerillas in the tunnels the US used soldiers dubbed tunnel rats.
Part of the Ho Chi Minh Trail was based in caves made of karst.
When Vietnam became a French colony again after the Second World War, the Communistic Viet Minh started to dig tunnels close to Saigon. After the French army left (they were defeated at Dien Bien Phu) the tunnels were maintained to prepare for a possible war with South Vietnam would start. Ho Chi Minh, leader of North Vietnam, ordered the expansion of the tunnels after the Americans entered the war between the North and the South; the tunnels would be used by the Viet Cong. Systems of tunnels were not occupied temporarily for military purpose, but began to contain whole villages of people living permanently underground. The tunnel system contained a complete world below ground, featuring kitchens, hospitals, workshops, sleeping areas, communications, ammunition storage, and even forms of entertainment. The tunnels eventually became a target for American forces because the enemy not only hid in them, but further could strike anywhere in the vast range of the tunnel complex (hundreds of miles) without a single warning before disappearing again.
These tactics were also applied against the Chinese during the Sino-Vietnamese War. The Củ Chi tunnels, a complex of over 200 kilometres (120 mi) of tunnel systems, allowed NLF guerrillas during the Vietnam War to keep a large presence relatively close to Saigon.

Palestine Liberation Organization: During the Palestinian insurgency in South Lebanon in the 1970s, PLO leader Yasser Arafat instructed his top military commander Khalil al-Wazir (Abu Jihad) to construct a network of underground bunkers and tunnels under Beirut and the Ain al-Hilweh refugee camp to defend against a possible Israeli invasion. Wazir, who had previously travelled to China, Vietnam and North Korea, based this system on the Viet Cong's model, hiding huge quantities of military supplies and linking Beirut with the PLO's strongholds in Southern Lebanon. A Lebanese Army officer later said: 'We just do not know how many miles of these tunnels there are. Some are new, some are old. We have no maps. They may be booby-trapped. Who knows?'
The tunnels proved useful for the PLO in the 1982 Lebanon War against Israel, being essential in a surprise attack during the Battle of Sultan Yacoub where Palestinians captured three Israel Defense Forces soldiers, who were later exchanged for over 1,000 imprisoned Palestinians. Perhaps the most effective use of tunnels by the PLO were during the siege of the Ain al-Hilweh refugee camp, when the PLO managed to inflict relatively heavy losses on the IDF and considerably slow its projected advance towards Beirut. Israeli historian Gil'ad Be'eri has written:

The Refugee camps were heavily fortified, full of bunkers and fire positions. The Palestinian defence at Ein El Hilweh and other refugee camps was based on hand-carried anti-tank weapons such as the RPG (Rocket propelled grenade). (...) The IDF was not prepared for this kind of fighting, having at hand mainly armoured forces intended for use in open areas. The built-up area inhibited long-range weapons, created an equality between the tank and the RPG (often wielded by 13- or 14-year-old boys), and increased the number of Israeli casualties. (...) Palestinian resistance seriously disrupted the timetable of the planned rapid advance to Beirut. It took eight days before the final crushing of resistance in Ein El Hilweh. The method adopted by the army was to use loud-speakers to call upon the civilian population to move away, search the houses one by one, surround points of remaining active resistance and subdue them by overwhelming fire.
Imad Mughniyeh, one of Abu Jihad's most trusted lieutenants and member of Fatah's elite Force 17 during the 1982 Lebanon War, would go on to become a senior Hezbollah military commander and was instrumental in the construction of Hezbollah's own tunnel network leading up to the 2006 Lebanon War (see below).

Afghan War: An underground war was actively pursued in the Afghan War. Water pipes extend under the entire Afghan territory. In wartime, Afghans have used these tunnels to both hide and to appear suddenly behind the enemy force. To clear these tunnels, Soviet troops used explosives and gasoline. The most famous underground base of the Mujahideen and then the Taliban was Tora Bora; this tunnel system went to a depth of 400 meters and had a length of 25 kilometres (16 mi). To combat guerillas in Tora Bora, the United States used special forces.
Osama bin Laden had in 1987 established his base near the Afghan-Pakistani border, for his Afghan Arab fighters who would later form the core of al-Qaeda. The base was equipped with an extensive tunnel network constructed by al-Qaeda's military chief Mohammed Atef, later one of the masterminds of the September 11 attacks. In May and June 1987 Soviet forces attacked the base with heavy artillery, aerial bombardment and numerous ground assaults, in the Battle of Jaji. In the end, the Mujahideen successfully held their complex system of tunnels and caves named al-Masada just outside the village of Jaji, near the Pakistani border, from Soviet capture.

Bosnian War: Between May 1992 and November 1995, during the Siege of Sarajevo in the Bosnian Army built the Sarajevo Tunnel in order to link the city of Sarajevo, which was entirely cut off by Serbian forces, with the Bosnian-held territory on the other side of the Sarajevo Airport, an area controlled by the United Nations. The tunnel linked the Sarajevo neighbourhoods of Dobrinja and Butmir, allowing food, war supplies, and humanitarian aid to come into the city, and people to get out. The tunnel was one of the major ways of bypassing the international arms embargo and providing the city defenders with weaponry. The Sarajevo Tunnel is now converted into a war museum, with 20 metres (66 ft) of the original tunnel open for tourists visit.

21st century: Due to the prevalence of bunker-busting munitions and combined arms maneuver warfare there has been a simple lack of need for such operations since the mid 20th century, making tunneling extremely rare outside of insurgencies (which often cannot use either of the former).

Syrian Civil War: During the Syrian civil war, rebel groups like the Islamic Front, Al-Nusra and ISIS dug tunnels and used explosives to attack fixed military positions of the Syrian Armed Forces and allied militias. A notable example is the attack on the Air Force Intelligence Building in Aleppo where on 4 March 2015, rebel forces detonated a large quantity of explosives in a tunnel dug close to or under the building. The building suffered a partial collapse as a result of the explosion which was immediately followed by an armed rebel assault.

Lebanese-Israeli War: In July 2006, a group of Hezbollah terrorist operatives crossed from southern Lebanon into northern Israel killing three Israeli soldiers and abducting two, which started the Lebanese-Israeli war. Faced with Israeli's air attacks, Hezbollah needed to create a defensive system that would enable these rocket attacks to continue uninterrupted throughout any conflict with Israel. To do so they created an intricate system of tunnels and underground bunkers, anti-tank units, and explosive-ridden areas.
Hezbollah built a sophisticated network of tunnels with North Korean assistance, with close resemblance to North Korea's own network of tunnels in the demilitarized zone separating the two Koreas. The underground network included twenty-five kilometer tunnels, bunkers, fiber optics communication systems, and storerooms to hold missiles and ammunition. Its capabilities were extended by Iranian supply of advanced weaponry and in-depth training of Hezbollah terroristoperatives. Between December 2018 and January 2019, the Israeli military destroyed six tunnels built by Hezbollah along Israel's border during Operation Northern Shield.

Israel-Gaza Conflict: Sometimes the ongoing conflict between the Israeli Army and Islamist militants in Hamas-governed Gaza Strip is called a tunnel conflict.
In 2017, the Barrier against tunnels along the Israel-Gaza Strip border began to be built to prevent the digging of cross-border attack tunnels. On October 30 such tunnel was located within Israeli borders and was detonated.
Hamas has constructed an extensive network of tunnels under Gaza City and other populated areas of the Gaza Strip, sometimes called the Gaza metro. The network is over 500 km (300 mi) in length according to Hamas claims. According to experts, these tunnels serve multiple purposes for Hamas, including holding kidnapped hostages, smuggling goods, moving militants, storing weapons, and sheltering Hamas members and infrastructure. However, the location and use of military tunnels in densely populated areas have raised concerns about Hamas endangering civilians.