Question: Mark Stephens defended a man who served as a former cavalry officer in what Army?

Context paragraphs:
Samuel Whitside: Brigadier General Samuel M. Whitside was a United States Cavalry officer who served from 1858 to 1902.  He commanded at every level from company to department for 32 of his 43 years in service, including Army posts such a Camp Huachuca, Jefferson Barracks, and Fort Sam Houston, the Departments of Eastern Cuba and Santiago and Puerto Principe, Cuba, commanded a provisional cavalry brigade (consisting of the 10th and 5th Cavalry Regiments), a squadron in the 7th Cavalry Regiment, and a troop and platoon in the 6th Cavalry Regiment.  The pinnacle of his career was serving as the Commanding General of the Department of Eastern Cuba before retiring in June 1902 as a Brigadier General in the U.S. Army.

Risaldar-major: Risaldar-major was originally a cavalry officer of the British Indian Army, the rank was created in 1886 - a risaldar-major was the most senior risaldar (army rank equivalent to a captain) of the regiment.  The rank was a Viceroy's commissioned officer in the cavalry.

Alfred Iverson Jr.: Alfred Iverson Jr. (February 14, 1829 – March 31, 1911) was a lawyer, an officer in the Mexican–American War, a U.S. Army cavalry officer, and a Confederate general in the American Civil War.  He served in the 1862–63 campaigns of the Army of Northern Virginia as a regimental and later brigade commander.  His career was fatally damaged by a disastrous infantry assault at the first day of the Battle of Gettysburg.  General Robert E. Lee removed Iverson from his army and sent him to cavalry duty in Georgia.  During the Atlanta Campaign, he achieved a notable success in a cavalry action near Macon, Georgia, capturing Union Army Maj. Gen. George Stoneman and hundreds of his men.

Frederick Mears: Colonel Frederick Mears (May 5, 1878 – January 11, 1939) was the son of a career army officer.  Older brother Major Edward C. Mears also of the US army.  Mears was principal engineer of the Alaska Railroad.  Mears took advanced engineering courses at the Infantry and Cavalry School, located at Fort Leavenworth, Kansas and became a cavalry officer in the US Army.

The Carriage: "The Carriage" (or "The Coach" in some translations; Russian: Коляска) is a 1836 short story by Nikolai Gogol, one of his shortest works.  The story centers on the life of a former cavalry officer and landowner near a small Russian town.  After reading the story, Anton Chekhov wrote to Alexei Suvorin, "What an artist he is!  His 'Carriage' alone is worth two hundred thousand rubles.  Sheer delight, nothing less."

Philip St. George Cooke: Philip St. George Cooke (June 13, 1809 – March 20, 1895) was a career United States Army cavalry officer who served as a Union General in the American Civil War.  He is noted for his authorship of an Army cavalry manual, and is sometimes called the "Father of the U.S. Cavalry."  His service in the Civil War was significant, but was eclipsed in prominence by the contributions made by his famous son in law, J.E.B. Stuart, to the Confederate States Army.

Johann Sigismund Riesch: Johann Sigismund Graf von Riesch (2 August 1750 – 2 November 1821) joined the army of Habsburg Austria as a cavalry officer and, during his career, fought against the Kingdom of Prussia, Ottoman Turkey, Revolutionary France, and Napoleon's French Empire.  He became a general officer during the French Revolutionary Wars and held important commands during the War of the Second Coalition.  He displayed a talent for leading cavalry formations, but proved less capable when given corps-sized commands.  During the 1805 Ulm Campaign in the Napoleonic Wars, the French badly defeated his corps and forced it to surrender soon afterward.  From 1806 to his death in 1821, he was the Proprietor (Inhaber) of an Austrian cavalry regiment.

René Prioux: René Jacques Adolphe Prioux (April 11, 1879 – June 16, 1953) was a general of the French Army who served in both world wars.  A cavalry officer of great talent, Prioux rapidly rose through the officer ranks and commanded the Cavalry Corps of the First Army during the Battle of Belgium in May 1940.  He was captured by the Germans and spent two years as a prisoner of war.  Repatriated in 1942, Prioux came to be seen as a strong supporter of the Vichy regime and was consequently removed from a position of authority in the French Army by Charles de Gaulle, the leader of the Free French, after the landings in French north Africa by U.S. and British forces in November 1942.

Mark Stephens (solicitor): Mark Howard Stephens CBE (born 7 April 1957) is an English solicitor specialising in media law, intellectual property rights and human rights with the firm Howard Kennedy LLP.  Stephens studied law at North East London Polytechnic (now the University of East London), graduating in 1978.  After further study in Brussels he was admitted as a solicitor in 1982.  Stephens started his career as a lawyer providing advice to artists and soon established his own practice with a partner.  In 1987 Stephens helped defend the American artist J. S. G. Boggs from a counterfeiting charge.  He gained a reputation as "the patron solicitor of previously lost causes" following this case and others where he defended artists' freedom of expression, as well as representing the leaders of the miners' strike of 1984–85 and James Hewitt when allegations of his affair with Diana, Princess of Wales first emerged.

James Hewitt: James Lifford Hewitt (born 30 April 1958) is an English former cavalry officer in the British Army.  He rose to public prominence in the mid-1990s after he disclosed a romantic affair that he had engaged in with Diana, Princess of Wales, while she was still the wife of the heir to the throne of the United Kingdom, Prince Charles.

Supporting paragraphs: Mark Stephens (solicitor) James Hewitt
Answer: British Army