His sister was the suffragette and Sinn Féin member Charlotte Despard. She would remain highly critical of her brother throughout his career.
He joined the Navy in 1866. After attending the Eastman’s Naval Academy in Portsmouth he transferred, however, to the British Army as a lieutenant in the 8th (King's Royal Irish) Hussars in 1874.
After the war, he was Commander-in-Chief at Aldershot 1901-1907 after which tenure he was promoted to full general and made Inspector-General of the Army (1907-1912). In 1911 he was made an ADC General to H.M. the King.
From March 1912 to April 1914, he served as Chief of the Imperial General Staff but resigned following the Curragh Mutiny and was made again Inspector-General of the Army in which post he served at the outbreak of the war.
French was the natural choice as Commander-in-Chief of the British Expeditionary Force (BEF) in August 1914.
A man of hot temper, he argued with the Cabinet against Field-Marshal Lord Kitchener and General Sir Douglas Haig that the BEF should be deployed in Belgium, rather than Amiens, where both Haig and Kitchener believed it would be well placed to deliver a vigorous counter attack once the route of German advance was known. Kitchener argued that the placement of the BEF at Mons would result in having to abandon its position and much of its supplies almost immediately as the Belgian Army would be unable to hold its ground versus the Germans; given the solid belief in fortresses at the time, it is not surprising that French and the British cabinet disagreed with Kitchener on this issue.
After the BEF's first battles at Mons and Le Cateau, where as Kitchener predicted, it had to retreat from its position to avoid the danger of being flanked when the Belgian position failed, French was increasingly indecisive and more concerned with preserving his troops, even suggesting removing them to the Channel Ports, than aiding the French. He began a tentative withdrawal which threatened to break the line between French and Belgian armies and needed an unwanted emergency meeting with Kitchener on September 2 1914 to re-organise his thinking and direct the counter-offensive at the First Battle of the Marne. French was particularly upset by the fact that Kitchener arrived wearing his field marshal's uniform, he felt Kitchener was implying that he was French's superior and not simply a cabinet member, a fact he mentioned in a letter to Sir Winston Churchill. No one knows exactly what was said during the meeting, as neither man kept any record, but French became increasingly antagonistic towards Kitchener in the following months.
During the First Battle of Mons, French issued a series of hasty orders to abandon positions and equipment which were ignored by his sub-ordinate in charge of the II Corps of the BEF, General Sir Horace Smith-Dorrien. Smith-Dorrien instead mounted a vigorous defensive action, relieving the pressure and allowing the troops to re-organise, gather up their supplies and make a comfortable fighting withdrawal. Smith-Dorrien also ignored other orders from French which he considered to be unrealistic. Smith-Dorrien was removed from command after advocating a tactical withdrawal away from German lines at Ypres, following the first use of poison gas by German troops. Several days after this, French accepted the advice of General Plumer to perform a withdrawal almost identical to the one Smith-Dorrien had recommended.
French remained in command as major trenching began and oversaw the fighting at Neuve Chapelle and Ypres that finally destroyed the last of the original BEF. In 1915, he declined to co-operate with the French and after the failures at Aubers Ridge and, at Loos, the British offensive operations were almost halted. In December 1915, he was replaced by General Sir Douglas Haig.
French returned to England to be appointed Commander-in-Chief of the British Home Forces in December 1915 and oversaw the suppression of the Irish uprising in 1916. In January 1916, he was created 1st Viscount French of Ypres and of High Lake in the County of Roscommon.
The volunteers' intelligence operative had informed the unit that Lord French would be travelling in the second car of the armed convoy that comprised an outrider and three following cars which would bring Lord French from Ashtown railway station to the Vice-Regal Lodge in Phoenix Park, Dublin.
The plan was for Martin Savage, Tom Kehoe and Dan Breen to push a hay-cart halfway across the road and then, after the out-rider and the first car had passed, they would push it the rest of the way across the road, thereby completely blocking the path of the remaining vehicles. They had been informed that Lord French was to be in the second car and this car would be attacked with grenades, Mills Bombs and concentrated rifle fire.
As they pushed the hay-cart across the road their plan was almost foiled as a Royal Irish Constabulary (RIC) officer disturbed them, telling them to move on. One of IRA men lobbed a grenade at him, although it didn't explode it struck the police officer on the head, knocking him unconscious. The police officer was then dragged from the road and the attack went ahead as planned.
In the crossfire Dan Breen was shot in the leg and seconds later Savage fell mortally wounded after being hit by a bullet in the neck. He died in the arms of Dan Breen and his last words to Breen were "I'm done, but carry on....". Tom Kehoe and the wounded Dan Breen carried Savage's body from the road and back to Kelly’s Pub while the gunfight continued.
Two Dublin Metropolitan Police officers were also wounded in the gun battle. At this point the British military, including some wounded, began to withdraw from the scene and continued on towards Phoenix Park. Realising reinforcements would be on their way, the IRA unit then dispersed to safe houses in the Dublin area. Dan Breen was helped onto his bike by Paddy Daly who helped him to a safehouse in the Phibsboro' area, where he was attended to by the captain of the Dublin hurling team, Dr J.M. Ryan.