In a tranquil verge in the Belgian countryside 85 men lie in repose, British casualties of the Great War. Hyde Park Corner (Royal Berks) Cemetery, outside Ploegsteert, looks like thousands of memorials across Europe, a quiet and dignified resting place for those who made the ultimate sacrifice.

This site is different, though, and when you arrive at row B, plot 21, you begin to understand why. This marks the grave of Max Seller. Unlike the men he is buried alongside, he was not British but German. His headstone is different too, for while the others are engraved with a cross, Seller’s is etched with the Star of David. What quirk of history brought a German Jew to be interred with the very men he was sworn to kill?

This was the question German historian Robin Schäfer set out to answer after he stumbled across this curious grave site in 2012.

The author of Fritz and Tommy has researched World War I extensively but the mystery of Max Seller was one he could not shake and he knew he had to solve it.

“A number of German soldiers are buried in British cemeteries,” Schäfer explains. “That is not uncommon. The unusual and noteworthy thing, and what sparked my interest in the burial initially, is that Seller is buried side by side with his former enemy, not singled out or grouped together with other Germans. That is unique.”

If the conditions of Seller’s burial are unique, it is because the course of his life and the circumstances of his death were extraordinary. Seller was an astonishingly brave soldier who fell in an act of last-ditch heroism that was half-daring and half-mad.

His courage was such that even the British held him in esteem and accorded him a fitting funeral. The one place where his valour was not recognised was back home; his service to the Kaiser did not save his family when the Nazis eventually came to power.

Born in Gunzenhausen, Bavaria in 1890, Maximilian Seller and four siblings were raised alone by their mother Martha after the death of their merchant father. After leaving school, Seller worked as a textile merchant in Bayreuth. In 1910 he was assigned to the 5th Bavarian Infantry Regiment to complete his military service and one year later he left with the rank of Unteroffizier.

But war was only a few years away and in 1914, Unteroffizier Seller joined the frontline with the 7th Bavarian Infantry Regiment.

A shoulder wound from enemy fire put him in hospital for two months but when he returned, Seller was put in charge of 12th Company, a reflection of the promise he showed but also of the heavy casualties suffered by the 7th Infantry. In 1915, Seller was promoted to Leutnant der Reserve and later sent to Ploegsteert to lead trench raiding parties on the British.

June 24 proved to be Seller’s last stand. Schäfer recounts: “Leading his troops through the cornfields in heavy fog, the German raid ran into a British patrol in no man’s land between the trenches.

“A firefight developed and the element of surprise was lost. The British patrol withdrew and the Germans attacked. Yet now they were received by well-prepared British troops who greeted them with a hail of rifle fire, cutting the majority of the attackers down and dispersing the rest.”

One soldier remained. Up from the mud, out through the fog, this lone warrior came charging, barreling straight towards the British, all the while lobbing hand grenades at them.

It was an audacious attack and ended the only way it could have, with the German officer bayoneted on the parapet and thrown, mortally wounded, into the trench below.

Max Seller had given his life for Germany. He was 24 years old. None of his compatriots were there to see his sacrifice but his pluck impressed one of the British officers present. Sergeant-Major Victor Rathbone of King Edward’s Horse, recognising Seller as a fellow Jew, arranged for a halachic burial and saw to it that Seller was laid to rest beside his fallen British foes. In his gallantry, he had earned it.

Rathbone felt an affinity for Seller and wanted to inform his family of his passing. Through his brother in London, Rathbone arranged for Seller’s death to be reported in the Jewish Chronicle. The July 2, 1915 edition of the JC carried the news, with a pithy tribute to Seller from Rathbone: “He was a plucky chap and our fellows could not help expressing admiration at his effort to bomb us.”

By the end of the Great War, Seller was one of 12,000 German Jews who fell fighting for the Kaiser’s Empire. The Nazis, as they grew in prominence, worked to distort and hide evidence of such Jewish patriotism. In 1937, Seller’s only surviving sibling, Elsa, was arrested by the Gestapo for “racial defilement” after her relationship with a non-Jewish man was discovered. She committed suicide in her cell.

Schäfer was by now deeply connected to Seller’s story and made it his mission to correct what he deemed a mark of disrespect. Seller’s headstone, as Schäfer originally encountered it, lacked a Star of David. He set out to right this, enlisting the help of the German ambassador to Belgium and the Commonwealth War Graves Commission. After three years of lobbying a Magen David was finally carved into the stone last year.

Schäfer says: “Seller’s faith needed to be recognised, just as it was in 1915 when Sergeant-Major Rathbone made sure that Max was given a Jewish burial ceremony. I personally could not accept it in any other way. Because of the Shoah there is virtually no one left to remember and to mourn the German Jews of the Kaiser’s Army. Their war was as much a fight against the enemies of their country as it was against intolerance and exclusion within it. For this, we have an obligation to remember them — and a duty to remember the life of a brave soldier who died for his country.”

The historian feels he has finally made peace with the memory of Max Seller and believes his story teaches us the importance of brotherly love. Schäfer recites a wartime verse by German poet Heinrich Lersch: “I risked the bullets and the shrapnel-rain, and ran/ And fetched him in, and buried… an unknown fellow man/ My eyes deceived me, but my heart proclaimed the truth to me/ In every dead man’s countenance a brother’s face I see.”