If you are a resident of the U.K. or one of the Commonwealth members like Canada, you are most likely already aware of the Commonwealth War Graves Commission.
However, if you live in the United States but have family members who served in World War I or World War II in a military capacity through a Commonwealth country, this may be a new resource for you.
The Wikipedia entry gives a concise explanation about why the Commission was created:
The Commonwealth War Graves Commission (CWGC) is an intergovernmental organisation of six independent member states whose principal function is to mark, record and maintain the graves and places of commemoration of Commonwealth of Nations military service members who died in the two World Wars. The commission is also responsible for commemorating Commonwealth civilians who died as a result of enemy action during the Second World War.
Use the CWGC War search tool to find your family member.
Be aware that if you use a VPN, you may have to turn it off in order to access this website.
I discovered this site a couple years ago when researching for a friend. I tracked down the story that her ancestor died in a submarine sinking during WWII. It was true and he is commemorated on a monument at Tower Hill in London, info I found on this website.