Francisco Franco Bahamonde (] ; 4 December 1892 – 20 November 1975) was a Spanish general who ruled over Spain as a military dictator from 1939 until his death in 1975.
Spanish Testament is a 1937 book by Arthur Koestler, describing his experiences during the Spanish Civil War.
 Part II of the book was subsequently published on its own, with minor modifications, under the title "Dialogue with Death" (see below).
 Koestler made three trips to Spain during the civil war; the third time he was captured, sentenced to death and imprisoned by the Nationalist forces of General Franco.
 Koestler was at that time working on behalf of the Comintern and as an agent of the Loyalist Government's official news agency, using for cover accreditation to the British daily "News Chronicle".
Koestler had been detained in three jails in separate countries.
 In Spain, he was sentenced to death in 1936 for espionage under Francisco Franco's regime.
 Here, he witnessed many executions, and was held in solitary confinement.
 He was arrested in France a few years later and held in the Le Vernet Internment Camp for subversion.
 Koestler was released and fled to England, where he was held at Pentonville as a suspected illegal immigrant.
The Common Corps of the Armed Forces are Spanish military corps that are shared by all the branches of the Spanish Armed Forces providing specific professional expertise.
 The Common Corps are four: The Military Legal Corps, The Military Comptroller Corps, The Military Health Corps and the Military Music Corps.
 Currently 2,991 Officers and NCOs make up the Common Corps.
 The educational centres of the Common Corps are part of the Central Defence Academy
The Royal and Military Order of Saint Ferdinand (Spanish: "Real y Militar Orden de San Fernando" ), is a Spanish military order whose decoration, known as Laureate Cross of Saint Ferdinand (Spanish: "Cruz Laureada de San Fernando" ), is Spain's highest military decoration for gallantry.
 It is awarded in recognition of action, either individual or collective, to protect the nation, its citizens or the peace and security of the international community in the face of immediate risk to the bearer or bearers' life or lives.
 Those eligible are current and former members of the Spanish Armed Forces.
Amado Granell Mesado (Burriana -Spain- November 5, 1898 - Sueca, May 12, 1972) was a Spanish military officer of the 20th century.
 He participated in the Spanish Civil War framed in the Spanish Republican Army and later went to France, where he joined the French Foreign Legion who fought against Nazi Germany during World War II.
 He headed the column of the 9th Company ""La Nueve"" of the 2nd Armoured Brigade, which consists of Spanish combatants, that was the first allied military unit that entered Paris after its occupation by the Wehrmacht.
 As such, he appeared on the cover of the newspaper "Libération" after the Liberation of Paris, and met with the leader of French Resistance, Georges Bidault.
Facundo Melgares (1775, Caravaca, Murcia, Spain - unknown) was a Spanish military officer who served as both the last Spanish Governor of New Mexico and the first Mexican Governor of New Mexico.
 Melgares was, like most of the officials of the Spanish crown in his time, a member of the Spanish upper class.
 He is described as a "portly man of military demeanour" and as "a gentleman and gallant soldier".
Antonio Ricardos Carrillo de Albornoz (1727, Barbastro – 13 March 1794) was a Spanish general.
 He joined the army of the Kingdom of Spain and fought against Habsburg Austria, the Portugal, and the First French Republic during a long military career.
 By embracing the Spanish Enlightenment, he earned the displeasure of conservative elements of society.
 He played an active role in reforming the Spanish military.
 Upon the outbreak of the War of the Pyrenees in 1793, the king sent him to command in Catalonia.
 He invaded Rousillon where he won several victories over the French.
 After his death in early 1794, the war went badly for Spain.
Marcos José de Garro Senei de Artola, nicknamed "El Santo" ("The Saint"), (1623–1702) was a Spanish military man who served in many positions in the colonial administration of the Spanish Empire.
 He served as governor of Tucumán from 1675–1678, governor of Buenos Aires from 1678–1682 and governor of Chile from 1682-1692.
 In Spain, he was military commander of the garrison at Gibraltar and Captain General of the Basque Country, a charge which he held until his death in 1702.
 In the colonies, his nickname was ""El Santo"" ("The Saint") for his religious piety.
 He is most well known for his successful attack on the competing Portuguese settlement at Colonia del Sacramento, constituting the first Spanish capture of the town.
Tomás Garicano Goñi (1919 – 1988) was a Spanish military lawyer, governor and politician, who served as interior minister during the Franco regime.

Question: Koestler was sentenced to death under the regime of which Spanish military dictator?
Answer: Francisco Franco Bahamonde