Trench warfare is a form of occupied fighting lines, consisting largely of trenches, in which troops are largely protected from the enemy's small arms fire and are substantially sheltered from artillery. It has become a byword for attrition warfare, for stalemate in conflict, with a slow wearing down of opposing forces.

Trench warfare occurred when a military revolution in firepower was not matched by similar advances in mobility, resulting in a grueling form of warfare in which the defense held the advantage. In World War I, both sides constructed elaborate trench and dugout systems opposing each other along a front, protected from assault by barbed wire. The area between opposing trench lines (known as "no man's land") was fully exposed to artillery fire from both sides. Attacks, even if successful, often sustained severe casualties as a matter of course.

Field works are as old as armies. Roman legions, when in the presence of an enemy, entrenched camps nightly when on the move. Similar measures, from Frederic the Great's camp at Bunzelwitz, to Arthur Wellesley's with his defense lines at Torres Vedras, to the French lines of Weissenburg, were frequently used.

Daniel Robert Snow (born 3 December 1978) is an English television presenter. He has presented and appeared in many popular history-related programmes for the BBC and is the "History Hunter" for The One Show.

Dan Snow is the youngest son of Peter Snow, BBC television journalist, and Ann MacMillan, Managing Editor of CBC London Bureau. Dan therefore has joint British/Canadian citizenship. Through his mother, he is the nephew of Canadian historian Margaret MacMillan, and a great-great-grandson of British Prime Minister David Lloyd George. One of his father's cousins is the Channel 4 news reporter Jon Snow.

Snow was educated at Barnes Primary School and St Paul's School, an independent school in Barnes in south London, where he was Captain of the School, followed by Balliol College at Oxford. He rowed three times in the University Boat Race, winning in 2000 and losing a controversial race, when president, in 2001. He received a double first-class honours degree in Modern History.

In 2003, Snow and his father made a programme on El Alamein to commemorate the 60th anniversary of the battles and followed this up with an eight-part series on BBC2 in 2004 called Battlefield Britain. This won a BAFTA award for special effects. The same year Snow won a Sony award as one of the presenters on LBC Boat Race coverage.

World War I (WWI), which was predominantly called the World War or the Great War from its occurrence until 1939 (World War II), and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918. It involved all the world's great powers, which were assembled in two opposing alliances: the Allies (based on the Triple Entente of the United Kingdom, France and Russia) and the Central Powers (originally centred around the Triple Alliance of Germany, Austria-Hungary and Italy; but, as Austria–Hungary had taken the offensive against the agreement, Italy did not enter into the war). These alliances both reorganised (Italy fought for the Allies), and expanded as more nations entered the war. Ultimately more than 70 million military personnel, including 60 million Europeans, were mobilised in one of the largest wars in history. More than 9 million combatants were killed, largely because of enormous increases in lethality of weapons, thanks to new technology, without corresponding improvements in protection or mobility. It was the sixth-deadliest conflict in world history, subsequently paving the way for various political changes such as revolutions in the nations involved.