Tony Gillam asked me to post a message here. I'll forward any replies to him.
Tony Gillam wrote:
Caro disappears from the German chess magazines in spring 1911 and nothing is known about him until his death. Where was he for 9½ years and why wasn't he playing chess?
If he was in Germany 1914-18, was he interned and if so, where? There was a big internment camp for British citizens at Ruhleben. There is an online list of the inmates and there are some Caros, but I couldn't find Horatio.
Someone mentions the many Caros living in the Bow/Poplar area in 1920 when Caro died. Were any of them his siblings? Do we have an address (we could then look things up on the electoral registers). I established today that Horatio did not have a will in probate 1920-23, so I suspect he may have died penniless and that increases the chances that he may have been living with a brother or sister, or other relative.
The earliest reference I can find to Caro in print, is in an article by Cordel on the Knight's Gambit in the August 1883 issue of the Deutsche Schachzeitung. At that time he was already "our young Berlin chess friend". Caro is credited with some analysis. The reason his name is associated with the Caro-Kann Defence (Kann was a Viennese who is said to have first played the defence, or perhaps we should say the first to be credited with it) is because of an article in the chess column of a Berlin newspaper called the Taegliche Rundschau in 1886. This article remains to be located (I believe the newspaper, for that year, is currently "lost").
Tony Gillam