In warfare, infiltration tactics involve small independent light infantry forces advancing into enemy into rear areas while bypassing enemy front line strongpoints, possibly isolating them for attack by follow-up troops with heavier weapons. Soldiers take the initiative to identify enemy weak points and choose their own routes, targets, and moments and methods of attack; this requires a high degree of skill and training, and can be supplemented by special equipment and weaponry to give them more options.
Forms of these tactics were used by skirmishers and irregulars, dating back to classical antiquity, but only as a defensive or secondary tactic; decisive battlefield victories were achieved by shock combat tactics with heavy infantry or heavy cavalry, typically charging en masse against the enemy's primary force. By the time of early modern warfare, defensive firepower made this tactic increasing costly. When trench warfare developed to its height in World War I, most such attacks were complete failures. Raiding by small groups of experienced soldiers using stealth and cover was commonly employed and often successful, but these could not achieve any decisive victories.
Infiltration tactics developed slowly through World War I and early World War II, partially as a way of turning these harassing tactics into a successful offensive doctrine. At first, only special units were trained in these tactics, typified by German Stosstruppen (storm troops). By the end of World War II, almost all regular ground forces of the major powers were trained and equipped to employ forms of infiltration tactics, though some would specialize in this, such as rangers, commandos, airborne and other special forces, and forces employing irregular warfare.
While a specialist tactic during World War I, infiltration tactics are now fully integrated as standard part of the modern maneuver warfare, down to basic fire and movement at the squad and section level, so the term has little special meaning today.
Clandestine, espionage, or false flag operations may involve infiltration, but this is based on deception, rather than these infiltration tactics, which are based on battlefield maneuver and combat tactics.
Development during World War IEdit
These tactics emerged gradually during World War I. Several nations modified their existing tactics in ways that supported ideas that were later called infiltration tactics, with the German developments having the most impact, both during the war and afterwards.
As far back as the 18th century, Prussian military doctrine stressed maneuver and force concentration to achieve a decisive battle (Vernichtungsschlacht). The German military searched for ways to apply this in the face of trench warfare.
Among these was Willy Rohr, a Prussian captain serving in the Vosges mountains. Rohr was engaged in the long Battle of Hartmannswillerkopf (1914-1915), starting with two Pionier (combat engineer) companies. Such engineers often employed non-standard weapons and tactics compared the regular infantry. Rohr's initial efforts to use these as special advanced strike teams to break enemy lines for following troops to exploit achieved only limited success, with heavy losses. Rohr, working with his superiors, saw equipment improved, including the new steel helmets, ample supplies of hand grenades, flamethrowers, and supported by light mortars and machine guns. Results were still mixed, however. Rohr's analysis was that much more training was needed, both to better incorporate these weapons and to coordinate separate attacks as needed to achieve the overall operational goals. His analysis got the attention of the German High Command; starting in December 1915, Rohr was given the task of training the army in "modern close combat", and promoted to major. During the next two years, special stormtrooper detachments were created in divisions throughout the army; select men were sent to Rohr for training, who would then train their comrades on return to their original units. These tactics were expanded and refined by many in the German military command, effectively extending the Prussian military doctrine down to smallest units — specially trained troops maneuvered and massed to assault positions wherever opportunities were found.
Infiltration tactics are sometimes called "Hutier tactics", after German General Oskar von Hutier, even though his role in developing the tactics was limited. Hutier, along with his artillery commander Colonel Georg Bruchmüller, improved the use of artillery in ways that fit well with infiltration tactics. At that time, the conventional mass-wave tactics were typically proceeded by days of constant bombardment of all enemy positions, attempting to gain some advantage by simple attrition. In contrast, Hutier favoured brief but intense "hurricane" bombardments that allow the enemy little time to react and reinforce their line. The bombardment targeted enemy rear areas to destroy or disrupt roads, artillery, and command centres. This was done to suppress and confuse the enemy, and reduce their capability to launch effective counterattacks from secondary defence lines. For maximum effect, the exact points of attack remained concealed until the last possible moment, and the infantry attacked immediately following the short bombardment.
The German stormtrooper methods involved men rushing forward in small groups using whatever cover was available and laying down covering fire for other groups in the same unit as they moved forward. The new tactics, intended to achieve surprise by disrupting entrenched enemy positions, aimed to bypass strongpoints and to attack the weakest parts of an enemy's line. Additionally, they acknowledged the futility of managing a grand detailed plan of operations from afar, opting instead for junior officers on the spot to exercise initiative.
Due to the extensive training needed, stormtroopers remained as elite special troops. Regular infantry with heavy weapons would follow up, using more standard tactics, reducing the now isolated and weakened enemy strongpoints with flank attacks, as the stormtroopers continued the advance beyond them. Reserve troops following these had to consolidate gains against any enemy counterattacks.
One of the problems of World War I was that the ground was so devastated that moving up reserves and materiel was difficult, allowing the enemy time to regroup. Thus, though they were far more successful than traditional attacks, they tended to bog down before a war-winning breakthrough was achieved.
The Germans employed and improved infiltration tactics with increasing success in a series of smaller to larger battles, at first defensively in counterattacks as part of Germany's defence in depth, and then offensively, leading up to the Battle of Caporetto against the Italians in 1917, and finally the massive German Spring Offensive in 1918 against the British and French. (General Hutier led the German 18th Army, which had the farthest advance in this offensive, thereafter associating his name with infiltration tactics in Western Europe.) However, after a stunningly rapid advance, the offensive failed to achieve a breakthrough dividing the French and British as planned; German forces stalled after outrunning their supply, artillery, and reinforcements, which could not catch up over the shell-torn ground left ruined by Allied attacks in the Battle of the Somme in 1916. The exhausted German forces were soon pushed back in the Allied Hundred Days Offensive, and the Germans were unable to organise another major offensive before the war's end.
In post-war years, although information on "Hutier tactics" were widely distributed in France, the US, and Britain, most generals were skeptical about these new tactics, given the overall German defeat. In Germany, infiltration tactics were integrated into the Reichswehr and the Wehrmacht. Felix Steiner, former officer of the Reichswehr, introduced the principle of stormtroopers into the formation of the Waffen-SS, in order to shape it into a new type of army using this tactic. When combined with armoured fighting vehicles and aircraft, this contributed to what would be called "Blitzkrieg" in the Second World War.
Similar tactics were proposed in various forms by other countries, or experimented with in individual battles, but these ultimately had little noted influence their respective military doctrines compared to the German's infiltration tactics.
The Russian general Aleksei Brusilov in the Brusilov Offensive of 1916 employed a surprise attack with limited artillery pre-bombardment, and achieved a breakthrough against Austro-Hungarian forces. However, the offensive overall was very costly for Russian troops. Brusilov's use of artillery was noted by German General Hutier, then serving on the Eastern Front. What influence Brusilov's tactics may have had on the Imperial Russian military was lost in the Russian Revolution of 1917.
The British Third Army employed tactics giving platoons more independence at the Battle of Arras in April 1917 (most notably the capture of Vimy Ridge by the Canadian Corps), following the reorganisation of British infantry platoons according to the new Manual SS 143. This still advocated wave attacks and taking strongpoints before advancing.
A form of infiltration tactics was proposed by French headquarters on 16 April 1915 in Note 5779, which stated that the first waves of infantry should penetrate as far as possible and leave enemy strongpoints to be dealt with by follow-up waves. These were partially adopted on 9 May 1915, the opening day of the Second Battle of Artois, by the French XXXIII Corps which advanced 4.5 kilometres (2.8 mi) in the first hour and a half of the attack. The problem was reinforcing and holding the gains against German counterattack. Overall, the battle was inconclusive, yet costly for the French in both men and matériel.
A young French infantry officer, Captain André Laffargue, put forward similar ideas in a pamphlet written in August 1915 Étude sur l’attaque dans la période actuelle de la guerre ("Study of the Attack in the Current Period of the War"). Laffargue based his proposals in particular on his experiences attacking immediately south of Neuville-Saint-Vaast on 9 May 1915 when commanding a company of 153rd Infantry Regiment. Laffargue was left wounded on the German front line but his regiment advanced another 1.5 kilometres (0.93 mi), only to be held up by two German machine guns. Laffargue's pamphlet focused primarily on the small-unit perspective, calling for mobile firepower to deal with local resistance such as machine guns and advocating that the first waves of an attack advanced in the intervals or gaps between centres of resistance, which should be temporarily neutralised on the edges by fire or heavy smoke. They would then be encircled and dealt with by successive waves. Had these methods been followed Laffargue suggests that the attack could have resulted in a complete breakthrough of the German defences and the capture of Vimy Ridge.
The crucial distinction between the forms of infiltration advocated by French headquarters and Laffargue as against those under development in the German army was that the French remained firmly wedded to the use of the attack by waves, despite the high casualties which could ensue. Laffargue put forward the view that the psychological support of the attack in line was necessary to enable men to advance against heavy fire. The French Army published Laffargue's pamphlet in 1915 (having already put forward a more developed version of his ideas in Note 5779) and the following year a commercial edition found wide circulation, but as informational rather than new training regulations. The British, like all combatants during 1914–1918, made frequent use of wave attacks and translated and published Laffargue's pamphlet in December 1915. The US Infantry Journal published a translation as The Attack in Trench Warfare in 1916.
In 1916, captured copies of Laffargue's pamphlet were translated and distributed by the German military. How much this may have influenced German infiltration tactics is not known; such influence has been dismissed by Gudmundsson. The Germans had started developing their own infiltration tactics in the spring of 1915, months before Laffargue's pamphlet was even published. 
Dien Bien PhuEdit
At the Battle of Dien Bien Phu, Major Marcel Bigeard, commander of the French 6th Colonial Parachute Battalion (6th BPC), used infiltration tactics in an attempt to defend the besieged garrison against the Viet Minh trench warfare tactics. Bigeard's parachute assault companies were supported by concentrated artillery and air support, and received help from tanks, allowing two companies (the 1st under Lieutenant René Le Page and the 2nd under Lieutenant Hervé Trapp) numbering no more than 180 men to recapture the important hilltop position of Eliane 1 from a full Viet Minh battalion, on the early morning of 10 April 1954.
Other parachute battalion and company commanders also used similar tactics during the battle.
- Graf Eberhard von Schwerin: Königlich preußisches Sturm-Bataillon Nr 5 (Rohr); Sporn, Zeulenroda (Thuringia) 1939, 166 pages
- Hermann Cron: Geschichte des Deutschen Heeres im Welkriege 1914-1918; Berlin 1937, p. 23
- Hellmuth Gruss: Die deutschen Sturmbataillone im Weltkrieg. Aufbau und Verwendung.; Berlin, 1939
- Corum, James S. (1992). The Roots of Blitzkrieg: Hans von Seeckt and German Military Reform. Lawrence, Kansas: University Press of Kansas. p. 30. ISBN 978-0-7006-0541-5.
- Citino, Robert M. (26 December 2007). The Path to Blitzkrieg: Doctrine and Training in the German Army, 1920-39. Stackpole Books. p. 16. ISBN 0811734579.
- "Instructions for the training of platoons for offensive action, 1917". Internet Archive. Retrieved 7 October 2017.
- Kraus Podcast. Kraus, Early trench tactics in the French Army, pp. 23–32.
- CSI Report No. 13: Tactical responses to concentrated artillery: Introduction (Combat Studies Institute, U.S. Army Command and General Staff College, Fort Leavenworth).
- Jones, "Infiltration by Close Order"
- CDS 333 "A Study of the Attack in the Present Phase of War: Impressions and Reflections of a Company Commander" (December 1915). Microsoft Word.
- Laffargue, The Attack in Trench Warfare.
- Gudmundsson, Stormtroop Tactics, pp. 193–196.
- Samuels, Martin Doctrine and Dogma, passim
- Samuels, Martin Command or Control?, passim
- Stormtroop Tactics, Appendix C and passim
- Samuels, Martin Doctrine and Dogma, 55
- Davidson, Vietnam at War, p. 265.
- Davidson, Phillip B. Vietnam at War: The History, 1946–1975. New York: Oxford University Press, 1991. ISBN 0-19-506792-4, ISBN 0-89141-306-5.
- Gudmundsson, Bruce I. Stormtroop Tactics: Innovation in the German Army, 1914–1918. New York: Praeger, 1989. ISBN 0-275-93328-8.
- Simon Jones, Infiltration by Close Order: André Laffargue and the Attack of 9 May 1915.
- Kraus, Jonathan. Early Trench Tactics in the French Army: The Second Battle of Artois May–June 1915. Farnham: Ashgate, 2013. ISBN 978-1-4094-5500-4.
- Kraus, Jonathan. Podcast: The Second Battle of Artois, May 1915: the new turning-point.
- Laffargue, André. The Attack in Trench Warfare Impressions and Reflections of a Company Commander by Capt. André Laffargue 153rd Infantry, French Army, Translated for the Infantry Journal by an Officer of Infantry. Washington, D.C.: The United States Infantry Association, 1916.
- Samuels, Martin. Doctrine and Dogma: German and British Infantry Tactics in the First World War. New York: Greenwood Press, 1992. ISBN 0-313-27959-4.
- Samuels, Martin. Command or Control?: Command, Training, and Tactics in the British and German Armies, 1888–1918. London; Portland, Oregon: Frank Cass, 1995. ISBN 0-7146-4570-2, ISBN 0-7146-4214-2.
- House, Jonathan M. Toward Combined Arms Warfare: A Survey of 20th-Century Tactics, Doctrine, and Organization. U.S. Army Command General Staff College, 1984. Available online (8 September 2016) or through University Press of the Pacific (Honolulu, Hawaii, 2002). ISBN 1-4102-0159-7.
- Pope, Stephen, Elizabeth-Anne Wheal, and Keith Robbins, eds. The Macmillan Dictionary of the First World War. London: Macmillan Reference Books, 1995. ISBN 0-333-61822-X.