Skirmish

Skirmishers are infantry or cavalry soldiers stationed ahead or alongside of a larger body of friendly troops. They are usually placed in a skirmish line to either harass enemy troops or to protect their own troops from similar attacks by the enemy. Skirmishers are generally lightly armoured for increased battlefield mobility and are usually armed with ranged weapons to attack the enemy from a distance.

Pre-modern
In ancient and medieval warfare, skirmishers typically carried bows, javelins, slings, and sometimes carried light shields. Acting as light infantry with their light arms and minimal armor, they could run ahead of the main battle line, release a volley of arrows, slingshots or javelins, and retreat behind their main battle line before the clash of the opposing main forces. The aims of skirmishing were to disrupt enemy formations by causing casualties before the main battle, and to tempt the opposing infantry into attacking prematurely, throwing their organization into disarray. Skirmishers could also be effectively used to surround opposing soldiers in the absence of friendly cavalry.

Once preliminary skirmishing was over, skirmishers participated in the main battle by shooting into the enemy formation, or joined in melée combat with daggers or short swords. Alternatively, they could act as ammunition bearers or stretcher-bearers.

Due to their mobility, skirmishers were also valuable for reconnaissance, especially in wooded or urban areas. During the gunpowder era, a skirmish line could discover the extent of the enemy front line.

In classical Greece, skirmishers had low status. For example, Herodotus, in his account of the Battle of Plataea of 479 BC, mentions that the Spartans fielded 35000 light armed helots to 5000 hoplites yet there is no mention of them in his account of the fighting.&lt;ref name="Greek Warfare p61"&gt;Greek Warfare, Myths and Realities, Hans van Wees p61&lt;/ref&gt; Often Greek historians ignored them altogether.&lt;ref name="Greek Warfare p61"/&gt; It was far cheaper to equip oneself as light armed as opposed to a fully armed hoplite - indeed it was not uncommon for light armed to go into battle equipped with stones.&lt;ref&gt;Greek Warfare, Myths and Realities, Hans van Wees p64p&lt;/ref&gt; Hence the low status of skirmishers reflected the low status of the poorer sections of society who made up skirmishers.&lt;ref name="Greek Warfare p65"&gt;Greek Warfare, Myths and Realities, Hans van Wees p65&lt;/ref&gt; Additionally, "hit and run" contradicted the Greek ideal of heroism. Plato gives the skirmisher a voice to advocate "flight without shame," but only to denounce it as an inversion of decent values.&lt;ref&gt;Greek Warfare, Myths and Realities, Hans van Wees p65, Laws 706c&lt;/ref&gt; Nevertheless, skirmishers chalked up significant, victories such as the Athenian defeat at the hands of the Aetolian javelin men in 426 BC and, in the same war, the Athenian victory of Sphacteria.&lt;ref name="Greek Warfare p65"/&gt;

Celts did not, in general, favor ranged weapons. The exceptions tended not to include the use of skirmishers. The Britons used the sling extensively, but for siege warfare, not skirmishing.&lt;ref&gt;The Ancient Celts, Barry Cunliffe pp 94-95&lt;/ref&gt; Among the Gauls likewise, the bow was employed when defending a fixed position.&lt;ref&gt;Caesar, De Bello Gallico, Book 7, XLI&lt;/ref&gt; The Celtic lack of  skirmishers cost them dearly during the Gallic Invasion of Greece of 279 BC,  where they found themselves helpless in the face of Aetolian skirmishing tactics.&lt;ref&gt;Peter Green, Alexander to Actium, p 133&lt;/ref&gt;

In the Punic Wars, despite the Roman and Carthaginian armies' different organizations, skimishers had the same role in both: to screen the main armies&lt;ref&gt;Hannibal's Last Battle: Zama and the Fall of Carthage, Brian Todd Carey p12 (Carthage) and p18 (Rome)&lt;/ref&gt;

The Americas
The Seven Years War and American War for Independence were two early conflicts in which the modern rifle began to make a significant contribution to warfare due to its advantage in range and accuracy over the smoothbore musket common among professional armies of the mid-18th century. Many of the men provided by the American colonists in both wars were frontiersmen serving in the militia--the Continental Army itself during the latter conflict was comprised largely of such irregular troops--participating in skirmishing tactics by firing from cover rather than the open field engagements of the day, largely influenced by Colonial experiences fighting natives. The character of Natty Bumpo in James Fennimore Cooper's novel The Last of the Mohicans was notably called La Longue Carabine by the French due to his skill with the long rifle common among the Colonials.

Napoleonic Wars
During the Napoleonic Wars, skirmishers played a key role in battles, attempting to disrupt the main enemy force by firing into their close-packed ranks, and by preventing enemy skirmishers from doing the same to friendly troops. As the skirmishers generally were spread out and were able to take cover behind trees, houses, towers and other obstacles, they were harder targets to hit with small arms and artillery fire. While muskets were the predominant weapon at the time, the British Army experimented with rifles, which previously during the wars in the Americas proved their far greater range and accuracy to deadly effect, increasing the effectiveness of the skirmisher in disrupting enemy movements and communication. In the American theater, American riflemen firing from cover once again contributed to heavy British casualties.

A feature of these wars was a trend to training line troops to adopt tactics that until then had been used only by skirmishers.&lt;ref&gt;History of the Art of War, Vol IV Hans Delbrück p449-51&lt;/ref&gt;

American Civil War
The treatise, New American Tactics, by General John Watts de Peyster advocated making the skirmish line the new line of battle, a revolutionary idea at the time.&lt;ref&gt;Randolph, pp.82-88&lt;/ref&gt; During the American Civil War, it was common for cavalrymen to dismount and form a skirmish line to delay enemy troops advancing towards an objective (for example, the actions of the Federal cavalrymen on the first day of the Battle of Gettysburg.)

Modern
By the late 19th century, the concept of fighting in formation was on the wane, and the distinctions between skirmishers and heavy infantry has now disappeared.