Thanks for the clues.
The Germans started the war advancing towards Lille, which is North West of your previous location, so I followed the railway line from there in that direction looking for roads crossing it.
When I got to road D674 there it was., just a nondescript open field now.
The nearest Village is Morhange which has a bloody history.
The Battle of Morhange saw the start of one of the bloodiest periods of the war for France, now largely forgotten, especially outside of France. Morhange was in Lorraine and was in a region annexed by the new nation of Germany after the Franco-Prussian War in 1871. Therefore Morhange was in Germany in 1914 and called Mörchingen. In the fighting here on 20th August 1914 the French lost more than 5,000 men, but it was just the start of a very dark period leading up to the blackest day on 22nd August 1914 when more than 22,000 French soldiers were killed in one day. By the close of the year the French had lost more than 300,000 killed on the battlefield; nearly a fifth of the total losses for the whole war in just the first few months.