Philippe began his military education at the École spéciale militaire de Saint-Cyr.
In June 1886 he was on the point of becoming an officer in the French army when his family was once again exiled by France's republican government.
At first he was placed under the tutelage of a Colonel de Parseval, under whose supervision he would later attend a military academy in Lausanne.
In Great Britain he entered the Royal Military College, Sandhurst, on the nomination of Queen Victoria in February 1887, completing his training there and developing an abiding interest in geography, topography, and the natural sciences.

He was attached for service to the King's Royal Rifle Corps, which was then serving in British India, but never held an actual commission in the British Army, in order to respect a French law forbidding Frenchmen from holding commissions in foreign armies without the permission of the French head of state.
Nevertheless he was ranked as a sub-lieutenant and served in India from January 1888 to March 1889, where he was a staff-officer to Lord Roberts, then Commander-in-Chief in India.

In October 1889, Philippe went to Switzerland to complete a course in military theory.
While there he fathered a son, Philippe Debien, by Nina, an actress working in the casino at Lausanne.
On his 21st birthday in February 1890 he left Switzerland by train with his friend Honoré d'Albert, 10th duc de Luynes, and entered Paris in violation of the law of exile of 1886.
There, he offered to perform his military service, as required by law.
Instead he was arrested and confined in the Conciergerie.
He was sentenced to two years imprisonment at Clairvaux, but was released after a few months and expelled back to Switzerland.

Drawn to explore the "unknown", Philippe asked Prince George, Duke of Cambridge, to send him to a military post in the Himalayas.
While in the East, he undertook a hunting and exploratory expedition in Nepal with his cousin Prince Henri of Orléans, went mountain-climbing in Tibet, and visited Afghanistan, Ceylon, and the Persian Gulf, before being posted back to Britain.

Prior to his imprisonment in France, Philippe had been unofficially engaged to his first cousin Princess Marguerite of Orléans, but the engagement was cancelled when Philippe's involvement with the Australian opera singer Nellie Melba was revealed.
 Melba was still married to Charles Nesbitt Armstrong, although they had lived apart for some years.
Armstrong filed for divorce from Melba on the grounds of adultery, naming Philippe as co-respondent; the case was eventually dropped.

In September 1890, Philippe accompanied his father on a two-month trip to the United States and Canada.
They visited the battlefields of the American Civil War, in which his father had fought, as well as Philadelphia, Washington, D.C., Richmond, Virginia, New York City, and Quebec.

On 12 November 1890, while in Philadelphia, Philippe joined the Pennsylvania Commandery of the Military Order of the Loyal Legion of the United States (MOLLUS) - a military society composed of officers who had served the Union in the American Civil War and their descendants, as a companion of the 2nd class - a membership category for the eldest sons of companions of the 1st class who were veteran officers.
 He was assigned MOLLUS insignia number 8262.
 Upon his father's death on 8 September 1894, he became a hereditary companion of the 1st class.

In December 1890, Philippe applied unsuccessfully to serve in the Russian Army.
In March 1893, he was elected a Fellow of the Royal Geographical Society.

In March 1894, Philippe went to Egypt and Palestine with his sister Hélène, Duchess of Aosta.
Then he went lion shooting in Abyssinia (modern Ethiopia).
In May 1894, he was attached to the Royal Buckinghamshire Hussars, a yeomanry regiment.
Philippe began his military education at the École spéciale militaire de Saint-Cyr. In June 1886 he was on the point of becoming an officer in the French army when his family was once again exiled by France's republican government. At first he was placed under the tutelage of a Colonel de Parseval, under whose supervision he would later attend a military academy in Lausanne. In Great Britain he entered the Royal Military College, Sandhurst, on the nomination of Queen Victoria in February 1887, completing his training there and developing an abiding interest in geography, topography, and the natural sciences.
He was attached for service to the King's Royal Rifle Corps, which was then serving in British India, but never held an actual commission in the British Army, in order to respect a French law forbidding Frenchmen from holding commissions in foreign armies without the permission of the French head of state. Nevertheless he was ranked as a sub-lieutenant and served in India from January 1888 to March 1889, where he was a staff-officer to Lord Roberts, then Commander-in-Chief in India.
In October 1889, Philippe went to Switzerland to complete a course in military theory. While there he fathered a son, Philippe Debien, by Nina, an actress working in the casino at Lausanne. On his 21st birthday in February 1890 he left Switzerland by train with his friend Honoré d'Albert, 10th duc de Luynes, and entered Paris in violation of the law of exile of 1886. There, he offered to perform his military service, as required by law. Instead he was arrested and confined in the Conciergerie. He was sentenced to two years imprisonment at Clairvaux, but was released after a few months and expelled back to Switzerland.
Drawn to explore the "unknown", Philippe asked Prince George, Duke of Cambridge, to send him to a military post in the Himalayas. While in the East, he undertook a hunting and exploratory expedition in Nepal with his cousin Prince Henri of Orléans, went mountain-climbing in Tibet, and visited Afghanistan, Ceylon, and the Persian Gulf, before being posted back to Britain.
Prior to his imprisonment in France, Philippe had been unofficially engaged to his first cousin Princess Marguerite of Orléans, but the engagement was cancelled when Philippe's involvement with the Australian opera singer Nellie Melba was revealed.  Melba was still married to Charles Nesbitt Armstrong, although they had lived apart for some years. Armstrong filed for divorce from Melba on the grounds of adultery, naming Philippe as co-respondent; the case was eventually dropped.
In September 1890, Philippe accompanied his father on a two-month trip to the United States and Canada. They visited the battlefields of the American Civil War, in which his father had fought, as well as Philadelphia, Washington, D.C., Richmond, Virginia, New York City, and Quebec.
On 12 November 1890, while in Philadelphia, Philippe joined the Pennsylvania Commandery of the Military Order of the Loyal Legion of the United States (MOLLUS) - a military society composed of officers who had served the Union in the American Civil War and their descendants, as a companion of the 2nd class - a membership category for the eldest sons of companions of the 1st class who were veteran officers.  He was assigned MOLLUS insignia number 8262.  Upon his father's death on 8 September 1894, he became a hereditary companion of the 1st class.
In December 1890, Philippe applied unsuccessfully to serve in the Russian Army. In March 1893, he was elected a Fellow of the Royal Geographical Society.
In March 1894, Philippe went to Egypt and Palestine with his sister Hélène, Duchess of Aosta. Then he went lion shooting in Abyssinia (modern Ethiopia). In May 1894, he was attached to the Royal Buckinghamshire Hussars, a yeomanry regiment.
Prince Philippe, Duke of Orléans (1869–1926)