It's a loose question. It could simply be the soldier who held the highest rank in the regular forces. He could be a head of government who promoted himself (Field Marshall Idi Amin and 7-star General Kim Jong Il.) He could be held as the highest-ranking soldier by act of congress/parliament (George Washington.) Then, there are the historical figures whose fame and status are difficult to contest (Julius Caesar, Alexander, and Genghis Khan.) For the Philippines, It would be Emilio Aguinaldo. He headed the revolutionary army after Bonifacio, and at 30 became the first elected President of a republic in the whole of Asia. I reckon one of the toughest call would be for the UK. Is it Alfred the Great? Nelson? Wellington? Montgomery (hehe)?
I took the question to be "Who was the greatest Military leader in your country"? The question doesn't have a date range... For me and Australia i would say Sir John Monash. General Sir John Monash, GCMG, KCB, VD (/ˈmɒnæʃ/; 27 June 1865 – 8 October 1931), was a civil engineer and an Australian military commander of the First World War. He commanded the 13th Infantry Brigade before the war and then, shortly after its outbreak, became commander of the 4th Brigade in Egypt, with whom he took part in the Gallipoli campaign. In July 1916 he took charge of the newly raised 3rd Division in northwestern France and in May 1918 became commander of the Australian Corps, at the time the largest corps on the Western Front. Monash is considered one of the best Allied generals of the First World War and the most famous commander in Australian history. - Wiki Monash helped to train the US soldiers entering the war. - "{7} The first significant action involving diggers and doughboys was the Australian attack on Hamel in July 1918.4 In that operation Lieutenant-General Sir John Monash was planning to eradicate a German salient to improve his line for future moves near Amiens. The Fourth Army commander, General Sir Henry Rawlinson, offered Monash the use of the recently-arrived 65th Brigade of the 33rd U.S. Division. The incorporation in the Australian battle plan of ten companies of infantry, from the 131st and 132nd Regiments, was to prove a controversial one." Americans with members of the Australian 37th Battalion at Villers-Bretonneux, June 1918, while attached for instruction. For my life time, i would say Sir Peter Cosgrove. - Chief of Defence Force and then Governor General of Australia...Universally well liked - The man that brought back the slouch hat when it was becoming obseleted. He not only ordered the Army to wear a slouch hat, but also the Air Force and Navy...Something only a Chief of the Defence force can do. I've met him on several occasions and greets everyone like an old friend. Note his Vietnam medals and Combat badge. General Sir Peter John Cosgrove, AK, CVO, MC (born 28 July 1947) is a retired senior Australian Army officer who served as the 26th Governor-General of Australia, in office from 2014 to 2019. A graduate of the Royal Military College, Duntroon, Cosgrove fought in the Vietnam War, receiving the Military Cross in 1971. From 1983 to 1984, he was commander of the 1st Battalion, Royal Australian Regiment, and he later served as commander of the 6th Brigade and the 1st Division. Cosgrove rose to prominence in 1999, when he served as commander of the International Force for East Timor (INTERFET), which oversaw the peacekeeping mission in East Timor during its transition to independence. Cosgrove was Australia's Chief of Army from 2000 to 2002 and Chief of the Defence Force from 2002 to 2005, receiving corresponding promotions to lieutenant general and general. Cosgrove retired from active service following the end of his term as Chief of the Defence Force, and subsequently served as leader of a taskforce helping to rebuild communities in Queensland after Cyclone Larry in 2006. In January 2014, Cosgrove was named to succeed Dame Quentin Bryce as Governor-General of Australia. He was sworn in on 28 March 2014 and made a Knight of the Order of Australia on the same date. Cosgrove retired on 1 July 2019 and was succeeded by General David Hurley.
Thankyou for your question. Sir Thomas Blamey is Australia's only Field Marshall. Blamey is the fat bastard in the middle... There was debate a few years ago whether to posthumously award Monash the rank of Field Marshall...I don't think that went through.
Surprise surpise for Finland it was Mannerheim. He had lead in 1917 Finland to independence and then he led us to major victory in Winter War. His picture was hanging in every Finnish house. A Finnish survey taken 53 years after his death voted Mannerheim as the greatest Finn of all time.[6] During his own lifetime he became, alongside Jean Sibelius, the best-known Finnish personage at home and abroad.[4] Given the broad recognition in Finland and elsewhere of his unparalleled role in establishing and later preserving Finland's independence from the Soviet Union, Mannerheim has long been referred to as the father of modern Finland, and the New York Times has called the Finnish capital Helsinki's Mannerheim Museum memorializing the leader's life and times "the closest thing there is to a [Finnish] national shrine".generals.] Carl Gustaf Emil Mannerheim - Wikipedia
On his Iron Cross ribbons he has the 1939 Spangs to denote he'd been awarded the Iron Crosses in WW1. How could he as Finland was part of Russia then ? Were they awarded to him by the Germans in the following civil war ?
In the US, General John Pershing was promoted to General of the Armies. No insignia was devised by it was assumed by some to be 6 stars, although he continued to wear four. He is considered to be the "highest ranking" general in the US armed forces. In WWII, the "senior general" most likely would have been George Marshall, with an equally ranking admiral being Harold Stark until he was relieved in 1942 to be replaced by Ernest King. Marshall Stark King
Finland was part of Russia since 1808. In 1917 during the chaos in Russia on 25th of January the whites and communists started the Civil war. Mannerheim led the whites. Part By part the Whites conquered the country, and also the Germans landed in Finland and attacked the communists and took Helsinki. This is a guess but I think Mannerheim got the iron cross for leading the whites against communists.
It was a long process but in the end, Washington and Pershing were given six stars (General of the Armies) while Dewey became Admiral of the Navy. This congressional resolution also carried with it the presumption that Washington will be held as the senior general of the US armed forces. No American soldier of the union can outrank him.