General Edmund Glaise von Horstenau

Croat Ustashi with the head of Serbian Orthodox Priest, Drakulići, 7 February, 1942.
When speaking about the genocide Croats committed during the WWII when over 1,7 million of Serbs were killed (approximately half of them by Croat Ustashi and Islamofascists on the territory of former Yugoslavia, while the other half died fighting against fascists), it is easy to forget the rare men of honor on the enemy side, who were horrified by the crimes of their own.
Such is the unknown German soldier who was herded up along with 7,000 Serbs from Kragujevac in front of the German firing squad on October 20, 1941, because he refused to carry out the order and shoot into the defenseless mass. The seven thousand men, women and children were collected randomly, from school and streets, and killed in reprisal for 70 German soldiers who lost their lives while fighting with Serbian resistance forces. It was the swift application of the newly established law by the German occupier: 100 Serbian lives for 1 German soldier. Among many school children shot that day along with their teachers were also three Roma boys age 12-15, who refused to clean filthy Nazi boots.
Italian fascists stationed in Dalmatia (present-day Croatia) quickly turned into Serbian allies after witnessing Croat Ustasha bestiality. They were protecting Serbs and Jews even after Croat Fuhrer Pavelic personally complained to Hitler about Italians, demanding they send Serbs who managed to escape Pavelic's bloodbath back to Ustasha, so they can continue the “purification of Croatia.” Concerned over the happiness and the wellbeing of his favorite ally, Hitler promptly wrote to Mussolini who ordered his troops in Dalmatia to comply, but Italians remained defiant. Their General Mario Roatta later explained in his memoirs Italians refused to hand over Serbs and Jews to the Ustasha because “they would be interned at Jasenovac, with well-known consequences.”
The Ustasha won't refrain from killing, because when the order to spill blood is issued, rivers of blood will flow... every Ustasha is waiting for an order to attack the enemy, to butcher and destroy.
Ante Pavelic
Italian commanders initially provided food and protection, and later guns and ammunition to units of Serbian Royal army (Chetniks under the command of General Draza Mihajlovic) for defense against the Ustasha. At Trebinje (Bosnia and Herzegovina which during the WWII was also annexed by the fascist Croatia), an Italian military governor actually disarmed an Ustasha detachment emerging from a massive slaughter of Serbs and placed them under arrest.
Austrian General Edmund Glaise von Horstenau, a German Plenipotentiary in Croatia, didn't go as far as arresting his hideous allies for their crimes, but he kept sending devastating reports about the monstrous Croat Ustashi he openly detested to Berlin. Although those reports went largely unnoticed at the time, they have given us a first-hand account of the black abyss of Ustasha pathological hatred and an unexpected eyewitness on the enemy side.
Most important is the dedication, guns, bombs and sharp knives of Croatian Ustasha, who will clear and cut all that is rotten from the healthy Croat body. And then, let the world observe the murdered and burned corpses of traitors.
Ante Pavelic
Visiting the Croatian countryside previously inhabited by the Serbs, Von Horstenau left a harrowing report:
We saw no sign of [guerrillas] but there were plenty of ownerless horses and cattle, not to mention innumerable geese. At Crkveni Bok, an unhappy place where, under the leadership of an Ustase lieutenant-colonel, some 500 country folk from fifteen to twenty years had met their end, all murdered, the women raped and then tortured, the children killed. I saw in the River Sava a woman's corpse with the eyes gouged out and a stick shoved into the sexual parts. This woman was at most twenty years old when she fell into the hands of these monsters. Anywhere in a corner, the pigs are gorging themselves on an unburied human being. All the houses were looted. The "lucky" inhabitants were consigned to one of the fearsome boxcar trains; many of these involuntary "passengers" cut their veins on the journey.
As soon as he arrived to his post in fascist Croatia, in June of 1941, General began his report:
According to reliable reports from countless German military and civilian observers, during the last few weeks, in town and country, the Ustasha have gone raging mad.
In the Autumn of 1942, Horstenau concluded another report with his assessment of the Ustasha as: “the unspeakable swineishness of this gang of murderers and criminals.”
Upon hearing about the “internment camps” for Serbs, Jews and Roma, General demanded to be taken to one. Although he was not taken to one of the worst concentration camps of the WWII, Jasenovac, and the camp he was allowed to visit was cleaned up for the occasion, the impression it left on Horstenau is one of utmost disgust and horror:
We now went into the concentration camp in a converted factory. Frightful conditions. Few men, many women, and children, without sufficient clothing, sleeping on stone at night, pining away, wailing and crying. A camp commandant - in spite of the later, favorable judgment of the Poglavnik - a rogue; I ignored him but instead told my Ustase guide: "This is enough to make you puke."
And then worst of all: a room along whose walls, lying on straw which had just been laid down because of my inspection, something like fifty naked children, half of them dead, the other half dying. One should not forget that the inventors of the KZ were the British in the Boer War. However, such places have reached their peak of abomination here in Croatia, under a Poglavnik installed by us. The most wicked of all must be Jasenovac, where no ordinary mortal is allowed to peer in.
There is no doubt Horstenau was an enemy to Serbs -- though utterly disgusted with Ustasha “swineishness,” Austrian General never went any further than reporting about the carnage, in hope someone higher up in the chain of command will rein the repugnant Ustashas in. An old soldier who have fought for the second time in a World War against Serbs and Russians, Horstenau still preserved some measure of basic human decency:
The Croat Revolution was by far the bloodiest and most awful among all I have seen firsthand or from afar in Europe since 1917. Croat Ustashas had done more evil in a day than the Serbian regime had done in twenty years.
General von Horstenau wasn't the only Wehrmacht officer to complain about the Ustasha's barbarity and sadism in dispatches to Berlin. Field Marshal Wilhelm List, for example, also protested against the wickedness of their Croat allies, as did many others.
German reports of Croat atrocities, contrary to the expected pride and smug superiority, contained descriptions such as “nauseating” and “disgusting.” German investigators excavating Serbian mass grave titled the illustrated catalog of headless bodies and mutilated corpses, What the Ustasha Did At Bjelovar. A Gestapo agent describes how the Ustasha had broken into an underground Orthodox Church (which Pavelic and Croatian WWII Cardinal Stepinac deemed “a political organization” rather than a faith), forced the worshippers to lay face down and speared them with bayonets like fish on a trident. “If a stop isn't put to this,” one German intelligence officer wrote with astonishing vehemence, “there won't be a Serb left in this country.”
Fifty years later, Franjo Tudjman and Croats who continued to nurture Pavelic's dreams and methods, prompted by the Vatican and New Germany, made sure there really isn't a Serb left in their country.