My grandfather was born in Belgium, emigrated to the U.S. in 1906 through Ellis Island, then moved to Pennsylvania. He later moved to Detroit, Michigan and started a family. In 1917 he went to Canada and was in The Overseas Expeditionary Forces. How would a person who seemingly has no ties to Canada or Britain, that I can find, be in the foreign military?
In 1917 if a Belgian living in the US wanted to fight for his country of birth then I suspect his thought process might be:
- How viable was it to sail to Europe and enlist for Belgium - I suspect it would cost a lot and, as @bgwiehle has commented, "civilian traffic across the Atlantic was severely curtailed by 1917, due to risk of attack (Lusitania, 1915) and appropriation of ships for military use"
- Would enlisting for the US get a soldier to the war soon - they declared war on 6 Apr 1917 but it seems US forces only began arriving in Europe during summer 1918
- How much would it cost to catch a train to Canada and enlist there instead - I suspect quite cheap and timely by comparison
The Canadian Soldiers of the First World War: 1914-1918 web site which is being rapidly expanded by Library and Archives Canada looks like something to keep an eye on:
The digitization of the Canadian Expeditionary Force (CEF) personnel service files is in progress. The original paper documents can no longer be consulted. However, digital reprography is available for those files that have not yet been prepared for digitization. Newly digitized files are added to the Soldiers of the First World War database, every two weeks until the project’s completion in 2016.
[Note: HistorySE might be a better venue for this question, if looking primarily for the motivations of American residents, either native-born or immigrant, that enlisted in foreign armies. G&FH SE answers focus more on documenting the individual, helping identify relevant records or providing resources for context].
Many of the volunteers in the CEF (Canadian Expeditionary Force, ~620,000 enlistments) were foreign-born - unsurprising in a "new" country, with a large proportion of immigrants. Patriotic feelings ran high, especially at the beginning of the war.
According to wikipedia's "Canadian_Expeditionary_Force" "By the end of the war in 1918, at least 'fifty per cent of the CEF consisted of British-born men'.
Googling american citizens in cef - yields a number of hits. According to at least one site, the blog "Roads to the Great War", 35,000 (~5% of CEF) Americans served in the CEF, many in "American Legion" contingents. U.S. citizenship was not at risk in WWI, and Americans were actively recruited in the earlier years of the war.
With 100th anniversary of WWI commemorations ongoing, many records are being made more available. Look not only for the official service papers through Library and Archives Canada, but look for histories of your grandfather's miltary units to flesh out what events he took part in.
Approx. 75,000 Americans and American related (immigrants, of American families, marriages, etc.) served in Commonwealth Forces including Canada in the two world wars. Your grandfather's story is logical and typical. Please see my website and book on the subject, which answers all of these questions and takes the story much further.