Editing Trench warfare (section)

=== World War II ===
In the decade [[Causes of World War II|leading up to World War II]], the French built the [[Maginot Line]], based on their experience with trench warfare in World War I. The Maginot Line was an extensive [[State of the art|state-of-the-art]] defensive system far superior to any previous trench system: a chain of massive constructions of concrete, iron, and steel fortresses, bunkers, retractable turrets, outposts, obstacles, and sunken artillery emplacements, linked by [[tunnel network]]s.  It covered the length of the Franco-German border and was {{convert|20-25|km}} wide. It was supported by numerous underground barracks, shelters, ammunition dumps and depots, with its own telephone network and [[narrow gauge]] railways with [[Armoured train|armoured locomotives]], backed up with heavy [[Railway gun|rail artillery]]. French military experts placed high value on the line, saying it would curb German aggression, as any invasion force would be halted long enough for French forces to mobilize and counterattack. Furthermore, [[French war planning 1920–1940|French military planning during the inter-war period]] believed that the line would force the [[Nazi Germany|Germans]] to invade Belgium. This would allow any future conflict to take place off of French soil. By bypassing the Maginot Line and fighting the Belgian Army, it would allow the French military to move its best formations to counter. In the [[Battle of France]], Germany invaded Belgium and the best Anglo-French forces moved to meet them as planned. However, the Germans had only recently changed their plans from what the French had anticipated would happen. Instead of an attack through central Belgium, the main German attack was delivered through the [[Ardennes forest]]. Inter-war French planning believed it would take the Germans 9 days to move forces through this area, and that it could be held by small forces. The German forces outpaced expectations and soon crossed into France between the main French forces and the Maginot Line. They then advanced towards the English Channel, and surrounded the Anglo-French armies. Small secondary German attacks concentrated at a few points in the Line had mixed success. The bulk of the Maginot Line was untouched, its garrisons withdrawn, and flanked. Due to the lack of combat, much of it has survived.

The return of [[Maneuver warfare|mobile warfare]] in World War II reduced the emphasis of trench warfare, as defenders commonly lacked the time to build up such battlefield defences before they were forced to redeploy, due to the more rapidly-changing strategic situation. But trench systems were still effective, wherever mobility was limited, the front lines were static, or around known critical objectives that could not be bypassed. More quickly improvised [[defensive fighting position]]s, using "scrapes" or "foxholes", that can be supplemented by [[sand bag]]s, local materials, debris, or rubble, remain in common use. These are typically improved and expanded by the defenders, eventually becoming full trench systems, if given enough time and resources.

In the [[Winter War]], the [[Mannerheim Line]] was a system of flexible field fortification for the defending Finns. While having very few bunkers and artillery compared to heavy defence lines like the [[Maginot Line]], it allowed defensive platoons to regroup between field fortifications ([[Field fortifications|wood-earth firing posts, dugouts and pillboxes]]) instead of locking them into bunkers, while forcing the invaders to attack trenches as in World War I without armor and direct fire support. It caused heavy losses to the Soviets and repelled them for two months.<ref>{{Cite book|title=The Árpád-line|last=Szabó|first=János J.|publisher=Timp|year=2002|isbn=963-204-140-2|location=Budapest|pages=6–67}}</ref>

[[File:The British Army in North Africa 1940 E932.jpg|thumb|A British trench mortar post in North Africa, 1940]]
[[File:62. armata a Stalingrado.jpg|thumb|upright=1.0|[[Soviet Union|Soviet]] soldiers running through the ruins of [[Battle of Stalingrad|Stalingrad]], 1942]]

At the [[Battle of Sevastopol]], [[Red Army]] forces successfully held trench systems on the narrow peninsula for several months against intense German bombardment. The Western Allies in 1944 broke through the incomplete [[Atlantic Wall]] with relative ease through a combination of amphibious landings, naval gunfire, air attack, and [[airborne troops|airborne]] landings. Combined arms tactics where infantry, artillery, armour and aircraft cooperate closely greatly reduced the importance of trench warfare. It was, however, still a valuable method for reinforcing natural boundaries and creating a line of defence. For example, at the [[Battle of Stalingrad]], soldiers on both sides dug trenches within the ruins; as well in the [[Battle of Hurtgen Forest]], both American and German soldiers also dug trenches and [[Fox hole|foxholes]] in the rugged woods of the forest which led to continuous stalemates and failed offensives that lasted for months, which was reminiscent of the trench warfare of World War I. The [[Battle of the Scheldt]], due to the geography of the battle field greatly involved the use of trench warfare. In addition, before the start of the [[Battle of Kursk]], the Soviets constructed a system of defence more elaborate than any they built during World War I.<ref>{{Cite web |date=2009-10-29 |title=Battle of Kursk |url=https://www.history.com/.amp/topics/world-war-ii/battle-of-kursk |access-date=2022-12-27 |website=www.history.com}}</ref> These defences succeeded in stopping the German armoured pincers from meeting and enveloping the salient.<ref>{{cite web |last1=Remson |first1=Andrew |last2=Anderson |first2=Debbie |url=http://geocities.com/armysappersforward/kursk.htm |title=Mine and Countermine Operations in the Battle of Kursk: Final Report |date=25 April 2000|access-date=2025-05-13 |url-status=dead |archive-url=https://web.archive.org/web/20091026215617/http://geocities.com/armysappersforward/kursk.htm |archive-date=October 26, 2009 }}</ref>

The [[Italian Campaign (World War II)|Italian Campaign]] fought from 1943 until the end of the war in Europe largely consisted of the Allies storming strongly fortified German lines which stretched from one coast, over the mountains to the other coast. When the Allies broke through one line, the Germans would retreat up the peninsula to yet another freshly prepared fortified line.
 
At the start of the [[Battle of Berlin]], the last major assault on Germany, the Soviets [[Battle of the Seelow Heights|attacked over the river]] [[Oder]] against German troops dug in on the [[Seelow Heights]], about {{convert|50|km|mi|abbr=on}} east of Berlin. Entrenchment allowed the Germans, who were massively outnumbered, to survive a bombardment from the largest concentration of artillery in history; as the Red Army attempted to cross the marshy riverside terrain they lost tens of thousands of casualties to the entrenched Germans before breaking through.

During the [[Pacific War]], the [[Empire of Japan|Japanese]] used a labyrinth of underground fixed positions to slow down the Allied advances on many Pacific Islands. The Japanese built fixed fortifications on [[Iwo Jima]], [[Okinawa Prefecture|Okinawa]], and [[Peleliu]] using a [[tunnel network|system of tunnels]] to interconnect their fortified positions. Many of these were former mine shafts that were turned into defence positions. Engineers added sliding armored steel doors with multiple openings to serve both artillery and machine guns. Cave entrances were built slanted as a defence against grenade and flamethrower attacks. The caves and bunkers were connected to a vast system throughout the defences, which allowed the Japanese to evacuate or reoccupy positions as needed, and to take advantage of shrinking interior lines. This network of [[bunker]]s, tunnels, and [[Pillbox (military)|pillboxes]] favoured the defence. For instance, the Japanese on [[Battle of Iwo Jima|Iwo Jima]] had several levels of honeycombed fortifications. The Nanpo Bunker (Southern Area Islands Naval Air HQ), which was located east of Airfield Number 2, had enough food, water and ammo for the Japanese to hold out for three months. The bunker was 90 feet deep and had tunnels running in various directions. Approximately 500 55-gallon drums filled with water, kerosene, and fuel oil for generators were located inside the complex. Gasoline powered generators allowed for radios and lighting to be operated underground.<ref>{{Cite book|title=A Tomb Called Iwo Jima|last=King|first=Dan|publisher=Pacific Press|year=2014|isbn=978-1500343385|pages=58–59}}</ref> The Japanese caused the American advance to slow down and caused massive casualties with these underground fixed positions. The Americans eventually used [[flamethrower]]s and systematic hand-to-hand fighting to oust the defenders.<ref name=WW2MMDb_Letters>{{cite web |url=http://www.worldwar2database.com/html/letters_from_iwo_jima.htm |title=Letters from Iwo Jima |publisher=World War II Multimedia Database |url-status=dead |archive-url=https://web.archive.org/web/20071212233438/http://worldwar2database.com/html/letters_from_iwo_jima.htm |archive-date=12 December 2007 |df=dmy }}</ref><ref name=BattleFleet_IwoDefense>{{cite web|url=http://www.battle-fleet.com/pw/his/Battle-Iwo-Jima-Defense.htm|title=Battle of Iwo Jima—Japanese Defense|work=World War II Naval Strategy|access-date=11 November 2018|archive-date=5 August 2017|archive-url=https://web.archive.org/web/20170805015433/http://www.battle-fleet.com/pw/his/Battle-Iwo-Jima-Defense.htm|url-status=dead}}</ref> The American ground forces were supported by extensive [[naval artillery]], and had complete [[air supremacy]] provided by [[U.S. Navy]] and [[United States Marine Corps|Marine Corps]] aviators throughout the entire battle.<ref>{{cite video | date = 19 March 1945 | title = Video: Carriers Hit Tokyo! 1945/03/19 (1945) | url =https://archive.org/details/1945-03-19_Carriers_Hit_Tokyo | publisher =[[Universal Newsreel]] | access-date = 22 February 2012 }}</ref>