Among his papers in the John McCrae House in Guelph is a letter he wrote on July 18, 1893, to Laura Kains while he trained as an artilleryman at Tête-de-Pont barracks, today’s Fort Frontenac, in Kingston, Ontario. “I have a manservant … Quite a nobby place it is, in fact … My windows look right out across the bay, and are just near the water’s edge; there is a good deal of shipping at present in the port; and the river looks very pretty.”

He was a resident master in English and Mathematics in 1894 at the Ontario Agricultural College in Guelph.

McCrae graduated in 1898. He was first a resident house-officer at Toronto General Hospital, then in 1899 at Johns Hopkins Hospital in Baltimore, Maryland. In 1900 McCrae served in South Africa as a lieutenant in the Canadian Field Artillery during the Second Boer War (1899 to 1902), and upon his return was appointed professor of pathology at the University of Vermont, where he taught until 1911; he also taught at McGill University in Montreal, Quebec.

In 1902, he was appointed resident pathologist at Montreal General Hospital and later became assistant pathologist to the Royal Victoria Hospital in Montreal, Quebec. In 1904, he was appointed an associate in medicine at the Royal Victoria Hospital. Later that year, he went to England where he studied for several months and became a member of the Royal College of Physicians.

In 1905, McCrae set up his own practice although he continued to work and lecture at several hospitals. The same year, he was appointed pathologist to the Montreal Foundling and Baby Hospital. In 1908, he was appointed physician to the Alexandra Hospital for Contagious Diseases. In 1910, he accompanied Lord Grey, the Governor General of Canada, on a canoe trip to Hudson Bay to serve as expedition physician.

When Britain declared war on Germany because of the latter’s invasion of neutral Belgium at the beginning of World War I (1914), Canada, as a Dominion within the British Empire, was at war as well. McCrae was appointed as Medical Officer and Major of the 1st Brigade CFA (Canadian Field Artillery). He treated the wounded during the Second Battle of Ypres in 1915, from a hastily dug, 8 foot by 8 foot bunker dug in the back of the dyke along the Yser Canal about 2 miles north of Ypres. McCrae’s friend and former militia pal, Lt. Alexis Helmer, was killed in the battle, and his burial inspired the poem, “In Flanders Fields”, which was written on May 3, 1915 and first published in the magazine Punch.

“In Flanders Fields” appeared anonymously in Punch on December 8, 1915, but in the index to that year McCrae was named as the author. The verses swiftly became one of the most popular poems of the war, used in countless fund-raising campaigns and frequently translated (a Latin version begins In agro belgico…). “In Flanders Fields” was also extensively printed in the United States, whose government was contemplating joining the war, alongside a ‘reply’ by R. W. Lillard, (“…Fear not that you have died for naught, / The torch ye threw to us we caught…”).

Though various legends have developed as to the inspiration for the poem, the most commonly held belief is that McCrae wrote “In Flanders Fields” on May 3, 1915, the day after presiding over the funeral and burial of his friend Lieutenant Alexis Helmer, who had been killed during the Second Battle of Ypres. The poem was written as he sat upon the back of a medical field ambulance near an advance dressing post at Essex Farm, just north of Ypres. The poppy, which was a central feature of the poem, grew in great numbers in the spoiled earth of the battlefields and cemeteries of Flanders. An article by Veteran’s Administration Canada provides this account:

For eight months the hospital operated in Durbar tents (donated by the Begum of Bhopal and shipped from India), but after suffering from storms, floods, and frosts it was moved in February 1916 into the old Jesuit College in Boulogne-sur-Mer.

On January 28, 1918, while still commanding No. 3 Canadian General Hospital (McGill) at Boulogne, McCrae died of pneumonia with “extensive pneumococcus meningitis” at the British General Hospital in Wimereux, France. He was buried the following day in the Commonwealth War Graves Commission section of Wimereux Cemetery, just a couple of kilometres up the coast from Boulogne, with full military honours. His flag-draped coffin was borne on a gun carriage and the mourners – who included Sir Arthur Currie and many of McCrae’s friends and staff – were preceded by McCrae’s charger, “Bonfire”, with McCrae’s boots reversed in the stirrups. Bonfire was with McCrae from Valcartier, Quebec until his death and was much loved. McCrae’s gravestone is placed flat, as are all the others in the section, because of the unstable sandy soil.

In 1918, Lieut. John Philip Sousa wrote the music to “In Flanders Fields the poppies grow” words by Lieut.-Col John McCrae.

McCrae was designated a Person of National Historic Significance in 1946.

The Cloth Hall of the city of Ieper (Ypres in French and English) in Belgium has a permanent war museum called the “In Flanders Fields Museum”, named after the poem. There are also a photograph and a short biographical memorial to McCrae in the St George Memorial Church in Ypres. In May 2007, to commemorate the 90th anniversary of the writing of his best-known poem with a two-day literary conference.

In May 2015, a statue of McCrae by Ruth Abernathy was erected on Green Island (Rideau River) in Ottawa, Ontario. McCrae is dressed as an artillery officer and his medical bag nearby, as he writes. The statue shows the destruction of the battlefield and, at his feet, the poppies which are a symbol of Remembrance of World War I and all armed conflict since. A copy of that statue was erected at Guelph Civic Museum in Guelph in 2015.