Katherine Mary Harley was born in Kent, UK, on 3rd May 1855. She was the the youngest of six daughters born to John Tracy William French, a Royal Navy Commander, and his wife, Margaret French, née Eccles.
Katherine's siblings included an elder sister, Charlotte, who became Charlotte Despard - 15 June 1844 – 10 November 1939 - a suffragist, socialist, pacifist, Sinn Féin activist, and novelist and and elder brother John ((28 September 1852 – 22 May 1925) who became the 1st Earl of Ypres and as Field Marshall Sir John French commanded the British Expeditionary Force in 1914.
Katherine's father died before she was born and when her mother was confined to an asylum in 1867; she was raised by relatives.
On 8th January 1877 Katherine married Colonel George Ernest Harley, CB, of Condover House, Shropshire, an officer in The Buffs. The couple had one son and two daughters. Her husband died on 22nd July 1907.
In 1910 Katherine joined the National Union of Women's Suffrage Societies (NUWSS) and became the honorary treasurer of the Midland Region. She was made president of the Shropshire branch of the NUWSS in 1913. Katherine was also a member of the Church League for Women's Suffrage. From 18th June to 26th July 1913 she proposed and organised the Great Pilgrimage - a march along six routes to converge on Hyde Park, London, where there was a rally.
During the First World War she helped to found and organise the Women's Emergency Corps - a service organisation founded in 1914 by Evelina Haverfield, Decima Moore, and the Women's Social and Political Union to contribute to the war effort of the United Kingdom during the conflict. The corps was intended to train woman doctors, nurses and motorcycle messengers. Mona Chalmers Watson became its honorary secretary. The Corps later evolved into the Women's Volunteer Reserve.
In 1914 Katherine volunteered to help the war effort by serving as a nurse with the Scottish Women's Hospitals for Foreign Service (SWH) in France, where she was awarded the Croix de Guerre. She became director of the hospital that Elsie Inglis's SWH organisation started in the Abbaye de Royaumont, 40 kilometres north of Paris, from January to April 1915 and then directed the hospital installed under tents in the Domaine de Chanteloup, Sainte-Savine, near Troyes, from June to October 1915.
In late 1915 Katherine transferred to Greece to nurse on the Balkan Front. In June 1916 she established a motorised ambulance unit attached to the Royal Serbian Army in Macedonia that operated near the front line, often at night, despite district orders to the contrary. In December 1916 she left the Scottish Women's Hospitals service to join an independent ambulance unit serving the civilian population of Monastir, Serbia (now in the Republic of North Macedonia).
She rented a house in Monastir after its capture, and it was there, on 7th March 1917, Katherine she was killed by shellfire. She was buried on 10th March in the city of Salonika and her funeral was attended by General Milne — the Commander of the British forces in the Balkans — and George, Crown Prince of Serbia. Katherine was buried in Lembet Road Military Cemetery, Slonika,.Thessaloniki in Greece, Grave Reference: O. 38
Her gravestone (see photograph above) bears the inscription "On your tomb instead of flowers the gratitude of the Serbs shall blossom there".
Katherine is commemorated twice in Condover parish church in Shropshire, UK - on a plaque on an oak screen that was erected in memory of Katherine and her husband, and on the parish's First World War memorial tablet which incorrectly names her "Katherine Ellen Harley". She is also remembered on the parish war memorial in the Trinity Chapel of St Mary's Church, Shrewsbury.