quality:corruption, structural:expansion
Precursors

Field works have existed for as long as there have been armies. Roman legions, when in the presence of an enemy, entrenched camps nightly when on the move. The Roman general Belisarius had his soldiers dig a trench as part of the Battle of Dara in 530 AD.

Trench warfare was also documented during the defence of Medina in a siege known as the Battle of the Trench (627 AD). The architect of the plan was Salman the Persian who suggested digging a trench to defend Medina.

There are examples of trench digging as a defensive measure during the Middle Ages in Europe, such as during the Piedmontese Civil War, where it was documented that on the morning of May 12, 1640, the French soldiers, having already captured the left bank of the Po river and gaining control of the bridge connecting the two banks of the river, and wanting to advance to the Capuchin Monastery of the Monte, deciding that their position wasn't secure enough for their liking, then choose to advance on a double attack on the trenches, but were twice repelled. Eventually, on the third attempt, the French broke through and the defenders were forced to flee with the civilian population, seeking the sanctuary of the local Catholic church, the Santa Maria al Monte dei Cappuccini, in Turin, also known at that time as the Capuchin Monastery of the Monte.

In early modern warfare, troops used field works to block possible lines of advance. Examples include the Lines of Stollhofen, built at the start of the War of the Spanish Succession of 1702–1714, the Lines of Weissenburg built under the orders of the Duke of Villars in 1706, the Lines of Ne Plus Ultra during the winter of 1710–1711, and the Lines of Torres Vedras in 1809 and 1810.

In the New Zealand Wars (1845–1872), the Māori developed elaborate trench and bunker systems as part of fortified areas known as pā, employing them successfully as early as the 1840s to withstand British artillery bombardments. According to one British observer, "the fence round the pa is covered between every paling with loose bunches of flax, against which the bullets fall and drop; in the night they repair every hole made by the guns". These systems included firing trenches, communication trenches, tunnels, and anti-artillery bunkers. The Ngāpuhi pā Ruapekapeka is often considered to be the most sophisticated and technologically impressive by historians. British casualties, such as at Gate Pa in 1864 and the Battle of Ohaeawai in 1845, suggested that contemporary weaponry, such as muskets and cannon, proved insufficient to dislodge defenders from a trench system. There has been an academic debate surrounding this since the 1980s, when in his book The New Zealand Wars, historian James Belich claimed that Northern Māori had effectively invented trench warfare during the first stages of the New Zealand Wars. However, this has been criticised by a few academics of the same period, with Gavin McLean noting that while the Māori had certainly adapted pa to suit contemporary weaponry, many historians have dismissed Belich's claim as "baseless... revisionism ". Others more recently have said that while it is clear the Māori did not invent trench warfare first —Māori did invent trench-based defences without any offshore aid— some believe they may have influenced 20th-century methods of trench design identified with it.

The Crimean War (1853–1856) saw "massive trench works and trench warfare", even though "the modernity of the trench war was not immediately apparent to the contemporaries".

Union and Confederate armies employed field works and extensive trench systems in the American Civil War (1861–1865) — most notably in the sieges of Vicksburg (1863) and Petersburg (1864–1865), the latter of which saw the first use by the Union Army of the rapid-fire Gatling gun, the important precursor to modern-day machine guns. Trenches were also utilized in the Paraguayan War (which started in 1864), the Second Anglo-Boer War (1899–1902), and the Russo-Japanese War (1904–1905).