It is difficult to avoid pathos on the 80th anniversary of the outbreak of World War II, which sent to the grave some 70 million people. Poland is where the horrors of WWII in Europe began. But for many Poles, the war wasn’t over until the last Russian soldier left their homeland in 1993. Poland proportionally lost more citizens than any other country.

Six million Poles perished, mostly at the hands of the German Nazis. Among them were three million Polish Jews, half of all victims of the Holocaust, targeted for annihilation for no other reason than that they were Jewish. Before the war, Poland was where 20% of all Jews in the world lived. By war’s end 90% of its Jewish population had been exterminated.

In a painfully ironic twist, it was Rafael Lemkin, a Polish Jewish legal scholar, who coined the term “genocide” and presented it to the League of Nations five years before the war started.

Thus, the lessons of that war are best remembered, and taught, by Poles and Jews acting together, even though the tragic outcome of the German aggression put an end to our two peoples being intertwined geographically in Poland, as had been the case for more than 800 years.

For the Poles, the war was never only about being the first to openly resist Hitler militarily, which the Poles did in response to the savage Nazi blitzkrieg to dominate Europe. Few remember that the war started as a joint act of aggression by the Soviet Union and Germany that lasted for almost two years. Barely two weeks into the German invasion, the Soviets attacked Poland from the east in fulfillment of the secret annex to the German-Soviet Ribbentrop-Molotov Pact.

The climax was the 1940 massacre of more than 20,000 Polish soldiers in Katyń — half of them reserve officers, including hundreds of Jews and Poland’s chief rabbi — by the Soviets acting as allies of Hitler.

Then came Hitler’s inevitable betrayal of Stalin, an invasion that saw the Nazis take the rest of Poland then penetrate deep into Russia. Stalin, now as a full-fledged Western ally, fought the Germans all the way to Berlin at an excruciating cost of human life.

Yet Poland wasn’t liberated by the Allies, but occupied yet again. It was betrayed at the Yalta Conference, which solidified the Cold War borders in Europe for decades. “Sold to the Soviet Union” is how the Poles felt.

Imagine the feelings of Polish Gens. Władysław Anders and Stanisław Maczek and their men.

Anders had joined the Western front with his famed 2nd Corps, responsible for breaking open the southern front at Monte Casino in Italy. He had allowed Jews in his army, and some of those Jewish troops were eventually dispatched to mandatory Palestine as part of an Allied force. They included future Israeli Prime Minister Menachem Begin, whom Anders afterward allowed, and even encouraged, to stay in Palestine to fight for the Zionist cause.

Maczek, meanwhile, led the Polish 1st Armored Division, remembered fondly to this day by so many French, Belgians and the Dutch for liberating their cities after his successful Falaise pocket campaign during the Battle of Normandy.

Despite these heroics, Poland found itself subjugated for half a century.

While the remaining scars still sting, it also makes the Poles naturally sympathetic to the world’s unfathomable betrayal of the Jews. It was Capt. Witold Pilecki, a Polish Army officer, who under the direction of the Polish underground state let himself be caught in a roundup to enter the Auschwitz concentration camp. Upon realizing the industrial-scale genocide of the Jews, he was the first to call on the free world through his smuggled reports to bomb the death camp — to no avail.

It was another Polish Army officer and resistance fighter, Jan Karski, who was among the first to report to the allies of the extermination camps in Europe and the destruction of the Warsaw ghetto. Yet amid the widespread reports of the mass slaughter of Europe’s Jews, the Allies refused to open their borders to Jewish refugees, refused to bomb the extermination camps or the railroads leading to them and refused to open the borders of British-mandated Palestine to allow Jews to escape Hitler to their Biblical homeland.

Of late we have grown accustomed to reading news reports of tensions between Poles and Jews, Poland and Israel. Yet on Sept. 1, Poles and Jews must be united in bearing witness to the atrocities of that world war as Hitler inflicted indescribable horror on the Polish nation in general, and on Polish Jews in particular, who bore the brunt of the largest genocide in human history.

It behooves us to jointly commit to historical memory and work together to remember Hitler’s victims, oppose every form of dictatorial oppression, condemn genocide wherever it rises and join together to fight growing anti-Semitism across the globe. Poles and Jews must together pledge to fight for and enforce the post-Holocaust cry of “Never Again.”

Maciej Golubiewski is the Polish consul-general in New York. Rabbi Shmuley Boteach is the founder of the World Values Network.