The same day, Boyle attended a rally at the Dawson City Athletic Association to sing "God Save the King" and declared his support for the war.

[8] During World War I, Boyle organised a machine gun company, giving the soldiers insignia made of gold, to fight in Europe.

In 1914, he wrote Sam Hughes, the minister of national defense, offering to raise at his own expense the machine gun company made up of Yukon miners.

[11] Morale problems began in the winter of 1914-1915 when the unit was not deployed to Europe immediately as promised, and were indeed not officially accepted as part of the Canadian Expeditionary Force until 18 February 1915.

On 27 July 1916, Boyle left Dawson City for London with the intention of negotiating a deal with the South African Goldfields Company to operate a gold-mining concession in Russia.

[13] In June 1917, Boyle undertook a mission to Russia on behalf of the American Committee of Engineers in London to help reorganize the country's railway system.

[15] Boyle's arrival at the Romanian court and his promise as he got on his knees to shake the queen's hand and to swear that he would never abandon her did much to lift her spirits.

[16] Marie later wrote of him: "I can honestly say that during that dark period of my life, Joe Boyle kept me from despairing...This strong, self-reliant man had been my rock on a stormy sea".

[17] One biographer of Queen Marie wrote of him: "An exaggeration of a man, Colonel Boyle reads today like a fictional hero created by his contemporaries to lighten the frustrations of defeat.

Were it not for the corroborating memoirs of his partner, Captain George A. Hill of the British Secret Service, we would write Boyle off as the wish fulfillment of a desperate queen looking for a twentieth-century version of Lancelot".

[18] Boyle, in cooperation with Captain George Hill, a Russian-speaking member of the British secret service, carried out clandestine operations against German and Bolshevik forces in Bessarabia and southwestern Russia.

[6] At a time when defeatism was rampant in Romania, Boyle together with Queen Marie and her lover, Prince Barbu Știrbey were the main advocates that the Allies would still win the war.

[17] Adding to Marie's woes, on 31 August 1918, the Crown Prince Carol, whose debauchery and dissolute ways had often worried her, impulsively deserted his Romanian Army unit and eloped to marry in Odessa Zizi Lambrino.

[17] Boyle provided the queen much emotional support as she later wrote that Carol's actions were "a staggering family tragedy which hit us suddenly, a stunning blow for which we were entirely unprepared.

Carol was banished to a remote Orthodox monastery located high up in the Carpathian Mountains with instructions that he would be released only after he agreed to annul his marriage to the commoner Zambrino and publicly apologise for deserting his unit.

Gortner, Boyle presents himself to Dowager Empress Maria Feodorovna at Yalta—as a Canadian White Army colonel—with news that George V is sending a British battleship HMS Marlborough to rescue the remaining Romanovs.

In the graphic novel Sous le soleil de minuit, published in 2015 by writer Juan Díaz Canales and artist Rubén Pellejero, Joe Boyle accompanies Corto Maltese in 1915 in his Alaskan adventure.