The Battle of the Somme was one of the largest military engagements of the First World War, and among the largest in history. Between July 1 and November 18, 1916, more than three million men took part in this battle, over one million casualties were recorded, around a third of which were fatalities. The first day of the battle alone saw approximately 70,000 casualties; 80 percent of which were British. In terms of its legacy, this battle came to epitomize the static, trench warfare most associated with the Western Front, and has become one of the most prominent symbols for remembrance in Britain and some of its former colonies . Given this status, and the fact that the British generally kept the most reliable records during the war (particularly from 1916 onward), the majority of statistical data relates to British actions in the battle, while estimates become more important in studying French and German involvement. Background and the initial attack The Somme Offensive was the planned Franco-British attack that would coincide with simultaneous offensives along the Balkan, Eastern, and Italian fronts, designed to stretch the Central Powers' forces across all European theaters of the war. The German offensive against the French at Verdun, however, had resulted in a stalemate and saw much of the French support redirected from the Somme; therefore, the British part in the offensive switched from a supporting to a leading role. Allied artillery lay down a week-long, constant bombardment upon the German front lines, in an attempt to clear a path through the barbed wire in no-man’s-land, disrupt supply lines, and destroy the enemy trenches. Despite dropping around 1.7 million shells on the enemy, much of the barbed wire remained intact, and the British had underestimated the depth and stability of the German trenches, which were 15 meters (50 feet) deep in some areas. Additionally, it is estimated that 30 percent of these shells failed to detonate. Approximately 120,000 men went over the top at 07:30hrs on July 1, 1916, in what became the costliest day in British military history. The advance was more perilous than anticipated, and the fortified German machine gun positions cut down thousands of British troops. British and French offenses in the south did make some progress in the opening stages of the battle, however the bulk of the force was held back by the Germans. This set the trend for the next five months, with heavy and slow attacks resulting in limited territorial gains. Technological advancements and new developments The Somme Offensive marked a major milestone in the history of warfare, as it saw the first ever deployment of tanks in the Battle of Flers-Courcelette, on September 15. Almost 50 Mark I tanks were sent to the Somme, although not all made it into the field. When deployed, the tanks achieved mixed results; a small number were able to push through no-man's-land and make some territorial gains, yet many became immobilized due to the rough, muddy terrain. To many military leaders at the time, the tanks were deployed prematurely and too sparsely to have a meaningful impact, and the element of surprise had been negated by their ineffectiveness; it would take another year before tanks would see significant success in the war. In contrast, aircraft played an invaluable role in the Battle of the Somme. Not only did fighters launch attacks and air raids on the enemy lines, but the reconnaissance obtained from the air gathered information on enemy movements, and radio messages helped to orchestrate artillery attacks in live time. The importance of this reconnaissance also led to air battles between fighters of the Imperial German Flying Corps and the Royal Flying Corps , the latter of which maintained aerial superiority throughout the war. The attritional bombardment seen on the Western Front, combined with the static nature of trench warfare, led to a "new" phenomenon coined as "shell shock" in 1915. While this is now clearly defined as a psychological issue and a form of PTSD, doctors in 1914 failed to diagnose or understand the problem correctly, often believing it to be a physiological result of artillery blasts on nervous system. By the time of the Somme Offensive, however, military officials were forced to take the problem more seriously, and a series of mental hospitals were established to help the affected recover, and return them to the front lines. Some estimates suggest that as many as two-fifths of all British casualties at the Somme were shell shock related. The battle draws to an end Five months of exhausting, attritional warfare and worsening winter weather eventually forced the Germans into retreat. From September onward, the Allies were able to capitalize on smaller gains to eventually push through the German lines to take strategic positions. Over these five months, a total of six miles (10 kilometers) was won along a 20 mile (32km) front. Although the offensive resulted in a tactical victory for the British and French forces, it was seen as a failure on the part of British military leaders, particularly Field Marshal Douglas Haig and General Henry Rawlinson, due to the heavy human toll. The Somme region would see further conflict in the latter stages of the war, during the German Spring offensive and Allied Hundred Days Offensive in 1918, including what is known as the Second Battle of the Somme. Today, there 243 British cemeteries in the Somme department of France , containing the remains of more than 153,000 soldiers; the identities of more than one-third of these men remains unknown. This text provides general information.