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In World War II Yugoslavia the Axis invasion unleashed age-old hatreds and sparked brutal internecine strife.

In January 1943 the German army launched a major offensive, codenamed Fall Weiss (“Case White”), to encircle an area in western Bosnia where the main force of Josip Broz Tito’s Yugoslav Partisans had taken refuge. It was the fourth of seven attempts the Germans made during World War II to stamp out Tito’s troublesome communist resistance group. The guerrillas were heading toward the border between Bosnia and Herzegovina, formed by the tumultuous Neretva River. Tito had ordered the destruction of all but one of the bridges in that sector; once his army had crossed, it would also destroy that span.

But a small German force racing west from Sarajevo captured the village where the last intact bridge stood, seemingly trapping the Partisans. The Germans had committed five of their own divisions and three divisions of their Italian allies— more than 100,000 men—to Fall Weiss. They were pursuing some 20,000 “bandits,” as the Germans called them, 3,500 of whom were sick or wounded. Marching with the Partisan column were some 40,000 refugees, most of them women and children, many of them ill, starving and shoeless in the dead of winter.

The Partisans were tough fighters and knew well the terrain through which they traveled, but their effort to reach and cross the Neretva looked hopeless. Harried by German aircraft during the day, the Partisan column traveled largely at night, but the weather was deadly, the Germans were pressing from behind, and the Neretva was now seemingly impassable. Tito had to improvise. He diverted the column to a demolished railroad bridge at Jablanica, 15 miles east of the German-held span, and by laying planks across the ruined girders constructed a narrow walkway that would support his oxcarts, troops and light artillery. Troops he sent back to fight a delaying action managed to drive the Germans back a few miles, and in early March the Partisans and refugees began crossing the river, all the while under attack by German aircraft. The operation took a week, and in the end some 25,000 Partisans and refugees reached relative safety on the other side of the Neretva. They had again broken out of a German trap.

But it was not just Axis troops with whom the Partisans had to contend. Waiting in ambush on the far bank of the Neretva were 12,000 Chetniks, members of a Serbian guerrilla army also dedicated to driving the Germans out of Yugoslavia, but dedicated even more passionately to killing Partisans. A commando unit Tito ordered across the river held off the Serbs long enough for the Partisan main force to cross, and then the outnumbered Chetniks themselves became the hunted. The Partisans chased the Chetniks back toward their homeland, Serbia, and few of them survived the pursuit. In Yugoslavia, then as now, few waited for the dish to turn cold before serving up revenge.

Yugoslavia in the early 1940s was fighting two wars at once—one against the Axis, the other a bitter civil war that pitted the communist Partisans against the royalist Chetniks, and Croatia’s fascist Ustase against both. It was the embodiment of English philosopher Thomas Hobbes’ state of “war of all against all,” and it was a far more vicious fight than the campaign against the invading Axis forces.

But Balkan conflicts have always been savage, and convoluted—Serbs vs. Croats; Eastern Orthodox Christians vs. Catholics, and both against Muslims; Slovenes, Montenegrins, Albanians and Macedonians all at each others’ throats. The region that became Yugoslavia (“Land of the South Slavs”) was the main battleground of the long-running clash between the Ottoman Empire and the Christian West and has an ancient and well-earned reputation for instability and internecine violence.

That penchant for violence stems largely from religion. Serbs are predominantly Eastern Orthodox, their cultural identity reinforced by their historic struggle against Islam and the unanimity of their orthodoxy. Croats and Slovenes are predominantly Roman Catholic; their ties are to the Vatican and to the Hapsburg rulers of the Austro-Hungarian Empire, who protected parts of Slovenia and Croatia from the invading Ottomans. During World War I the Croats fought alongside the Austrians against the Serbs who were fighting for the Allies, adding to the bitterness and hatred between the two people—both of whom speak variants of Serbo-Croatian. In Bosnia much of the original Christian population converted to Islam during the Ottoman period. This laid the foundation for intense hatred within Bosnia between remaining Christian Serbs and Muslim Bosniaks, who became especially vulnerable when the Balkan League drove the Ottomans out of the region in the years immediately before World War I. These same Christian-Muslim tensions have long bedeviled relations between Serbia and Kosovo, whose people are ethnically Albanian and overwhelmingly Muslim.

That these disparate and often violently opposed peoples became members of a single polyglot nation was the result of the 1919 Versailles Treaty. Though mindful that the June 1914 assassination in Sarajevo of Austrian Archduke Franz Ferdinand by the Bosnian Serb nationalist Gavrilo Princip had sparked World War I, in a mood of irrational optimism about nation-building the Great Powers cobbled Croatia, Serbia and Slovenia together into Yugoslavia and gave the new nation a king—Alexander I—chosen from the ranks of Serb nobility. Montenegro joined the others in 1921, the same year a terrorist gunned down the new country’s interior minister. In 1928 another fanatic shot five members of parliament, whereupon Alexander closed parliament and assumed dictatorial powers. A Croatian terrorist shot and killed the monarch on a street in Marseilles at the beginning of a trip to France in 1934. In Europe between World Wars I and II, Rebecca West noted in her book on Yugoslavia, Black Lamb and Grey Falcon, the word “Balkan” came to be a slur applied to brutal people everywhere.

Nazi Germany would have been wise to stay clear of the Yugoslav snake pit, but Adolf Hitler needed the Balkans. Germany already got much of its oil from the Romanian fields at Ploesti, and other resources from elsewhere in the Balkans. But what the Germans didn’t need was to divert military forces from their long-planned invasion of Russia. In 1940 Hitler tried to ensure the safety of his right flank by persuading Yugoslavia, Bulgaria and Romania to join the Tripartite Pact among Germany, Italy and Japan. The first to sign was Romania, while the others held back. Meanwhile, Italy’s Benito Mussolini, all ego and bluster, decided on his own to invade Greece. He used Albania as his staging area, sending 100,000 Italian troops across the Greek border in late October 1940. The invasion quickly stalled, however, because the Greeks knew their own mountains and how to use them to advantage: Sure-footed mules carried their light artillery along the ridge lines, and the Greek command ran well-coordinated surprise attacks by small units on the Italian columns threading through the valleys. Within two months the outnumbered, poorly equipped Greeks not only regained all the ground initially lost to the Italians, but also penetrated 20 miles into Albania. So much for ego and bluster.

The Greek defense was heroic and encouraging, but it was no use. The Italians and their incompetent leaders were one thing, the Wehrmacht quite another. In March 1941 Bulgaria joined the Axis pact. That put contingents of German troops into both Romania and Bulgaria, surrounding Yugoslavia and opening Greece to the Nazi attack. Within days the regent of Yugoslavia, Prince Paul, gave in and also signed the Tripartite Pact. Britain was pouring as many troops as it could spare from North Africa into Greece, hoping to preserve its bases in the eastern Mediterranean, but it was clear from the beginning they could do little more than slow the German advance. Then, two days after Prince Paul had signed the pact, a group of military officers in Belgrade threw out the regent, put his 17-year-old cousin Peter on the throne and repudiated the signing. Yugoslavia would not cave in to Germany.

Within hours the coup leaders were having second thoughts. Germany was a highly effective military machine. Yugoslavia was weak, deeply divided, with obsolete arms and little that could be called an air force. Who could help them? Britain was fighting for its life at home and in the North African desert. Greece was about to be invaded by a German army gathering in Bulgaria. Yugoslavia assured the Nazis it would continue to provide Germany with the natural resources it needed and had no aggressive aims. But it was too late. The Yugoslavs had annoyed Hitler; they would have to be punished. On April 6, 1941, Germany’s Operation Punishment began with the destruction of Belgrade from the air. That same day German, Italian and Hungarian armies crossed the border from all directions. Within days the young King Peter and what remained of his government had fled into exile, and Yugoslavia was in German hands. Estimates of Yugoslav deaths during the first day of the invasion run as high as 20,000. The Germans lost just 151 killed in the 11 days of fighting that followed.

The Germans, confident there would be little more opposition with which to contend, left behind four of their weaker divisions to occupy the country. They seem not to have noticed the small bands of Yugoslav officers and men that had melted into the mountains.

Among those officers was Colonel Dragoljub “Draza” Mihailovich, a Serb, a highly decorated World War I veteran and a dedicated royalist. In May 1941 Mihailovich established a base in the Serbian mountains and formed a resistance group known as the Chetniks, which began training the various ad hoc guerrilla bands that had sprung up following the German invasion. The Nazi assault had also prompted the Yugoslav Communist Party to call for popular action against the invaders, and longtime party organizer and decorated World War I veteran Josip Broz Tito, a Croat, was appointed commander of the party’s military force, the Partisans.

Mihailovich was initially under orders from the government-in-exile in London not to fight the Germans, if possible, so as not to provoke further retaliatory massacres of Yugoslav civilians. Tito had no such orders, and the Soviets were urging him to create as much trouble as possible in Yugoslavia in order to tie up German divisions that would otherwise be tearing across the Russian steppes. When Tito’s overtures to Mihailovich regarding joint operations against the Germans went nowhere, the two went their separate ways. Soon enough their mutual distrust turned to outright warfare, with Chetniks and Partisans firing on each other whenever they met.

But there was another side to this burgeoning civil war. Following the German invasion, the Nazis transformed the former province of Croatia into a puppet state under the control of the Croatian fascist party Ustasa. Fanatically Roman Catholic and rabidly anti-Serb and anti-Semitic, the Ustase, as its members were known, made genocide their official policy and, under the cover of the Nazi occupation, slaughtered some 300,000 to 750,000 Serbs (estimates vary widely), as well as thousands of Jews and Gypsies. To call it “slaughter” understates the Croats’ violence. They buried people alive, threw them into fires, gouged out eyes and cut off limbs, noses, breasts, ears and heads. The Serbs committed similar atrocities upon Muslims in the Sandzak region—the border between Bosnia and Serbia—while many Bosnian Muslims in Germany’s Handschar Waffen SS division butchered Serbs, Jews and Partisans. Nor were the Partisans innocent: They summarily executed scores of captured Germans, Chetniks and others they deemed fascists or “counterrevolutionaries.”

Accounts of this multifaceted civil war read like Jacobean revenge tragedy, but writ on a national scale. Children were forced to watch as parents were tortured and killed—and vice versa. Beheadings were common. Ancient remorseless hatreds, clearly, seethe beneath the surface of Balkan life. Add to this explosive mix the warring political ideologies of the 20th century—communism, fascism, the nostalgic remains of monarchism—and it isn’t hard to see why World War II sparked more than a predictable resistance conflict between Germans and Yugoslavs. In this land of blood feuds it opened the gates of hell.

While the fighting among Yugoslavia’s ethnic and political factions was genocidal, it was also a military conflict—one in which the Partisans were ultimately victorious. And the reasons for that victory are not difficult to discern.

The Chetniks lost their cachet and their effectiveness as they did less and less, forever waiting for the moment to strike, while Tito gained in popularity and in manpower. The Chetniks not only failed to vigorously attack the Germans but also collaborated with them and concentrated wholly on waging war against the Partisans. Every German reprisal against civilians, meanwhile, brought more recruits to the Partisans, and Tito accepted them from any ethnic group, any political persuasion, either gender, as long as they were willing to fight.

Both Chetniks and Partisans came to control large areas of countryside, while the Germans occupied the cities and larger towns. The Balkans are mountainous, the winters bitter and snowy; so the Germans brought in crack mountain divisions in an attempt to gain an advantage in the rugged countryside the locals knew so well. They made many attempts to surround Partisan forces, and succeeded, only to watch in frustration as the Partisans focused their entire power on the weakest point in the German line and broke out. The Partisans took weapons and uniforms—stripping off the insignia —from dead Germans and Italians.

As the war went on the Allies grew more interested in Yugoslavia’s various guerrilla groups. The British took an interest first—the Yugoslav government-in-exile was passing intelligence provided by Mihailovich and promoting the Chetniks. The Chetniks were also rescuing Allied airmen downed over Yugoslavia. An enthusiastic Winston Churchill parachuted a few Serbo-Croatian–speaking officers into the Yugoslav interior to assess the situation and arrange airdrops of food and equipment. Around 1943 the U.S. Office of Strategic Services (OSS), predecessor organization to the CIA, became active in the Balkan situation and began sending its own people into Yugoslavia— thereby exacerbating the turf war between British and American intelligence services that was already complicating the Allied war effort. Both agencies found out soon enough that Mihailovich was far more interested in killing Partisans than Germans, and the Partisans found that the Americans were far more effective at delivering supplies than the British. In 1943 the British delivered some 125 tons of food and supplies to the Partisans by air. In the same period the OSS, using a flotilla of fishing boats, tramp steamers and the like sailing from the Italian coast, delivered some 6,000 tons of supplies.

In the end what convinced the Allies to back Tito rather than Mihailovich was the simple fact that the Partisans were far more effective militarily than the Chetniks. That Tito was a Soviet-trained doctrinaire communist and a member in good standing of the Comintern mattered far less than the fact that he was an excellent tactician. His steadily growing army—which by the spring of 1944 numbered 300,000 —was tying down huge numbers of German troops. Indeed, so effective was Tito that the Germans put a large bounty on his head— 100,000 marks. They pursued him relentlessly and once came within an ace of capturing him; his train was leaving a station while German bullets whistled through the surrounding woods, whereupon the Allies spirited him out of the country for three months so he could plan the end game of the war in safety. Tito had become the indispensable man in the Balkans.

The Germans began to retreat from Greece through Yugoslavia in September 1944. The Russians by that time were advancing across the Danube, Tito’s Partisans had grown in strength to nearly 800,000, and the conflict in Yugoslavia was no longer a guerrilla war but a war of pitched battles. Most of the country was in Partisan hands, with the Chetniks controlling only the Serbian countryside. Because they remained inactive against the Germans, the Allies refused Mihailovich and his followers any more support. When the Russians crossed the Yugoslav border and encountered Chetnik troops, they disarmed them and turned them over to the Partisans. The next target was Belgrade, capital of the country and key to the rail lines north out of Yugoslavia. In October 1944 Partisan and Soviet troops fought a house-to-house battle through the city that lasted a week and killed 16,000 Germans.

The war had made Tito an international hero and the de facto ruler of Yugoslavia, prime minister of what soon became the Socialist Federal Republic of Yugoslavia. The kingdom was gone for good. But it would be a mistake to say Tito had won the war. The Germans were beaten, but the fighting in Yugoslavia wasn’t over. In mid-May 1945, a week after Germany surrendered to the Allies, the Partisans engaged the remnants of the Croatian Ustase and the Chetniks as they retreated toward the Austrian border in an attempt to surrender to the British. But the British promptly turned them back over to the Yugoslav, i.e. Partisan, authorities. What happened next has been the subject of argument ever since. By some it is known as the Bleiburg massacre, and estimates of the Ustase and Chetniks summarily executed by the Partisans run as high as 80,000. Others argue that no massacre really happened or, if it did, the numbers were much smaller. Among Croats, Bleiburg has become a pilgrimage site. To them it represents a balance to the Ustasa concentration camps, in which many thousands of Serbs, Gypsies and Jews died. Bleiburg, they insist, demonstrates that Croats, too, were victims who suffered in the war. The Partisans and their ideological heirs insist that Croat casualties were minor. Draza Mihailovich escaped the Bleiburg trap, but not Tito’s vengeance. Captured by Partisan forces, the Chetnik leader was tried for treason and war crimes and executed in July 1946.

The argument persists about whether Mihailovich, among others, was a Serb patriot or a war criminal. It is one more sign that the war is not over, indeed, that in the Balkans war is never over, that losses suffered in the 1300s still sting, and nothing is forgiven. In Zagreb, a Croatian city, Rebecca West wrote in 1937:

Were I to go down into the marketplace, armed with the powers of witchcraft, and take a peasant by the shoulders and whisper to him, “In your lifetime have you known peace?” wait for his answer, shake his shoulders and transform him into his father, and ask him the same question, and transform him in his turn to his father, I would never hear the word “Yes,” if I carried my questioning of the dead back for a thousand years.

While Yugoslavia knew relative peace in the decades following World War II, Tito’s death in 1980—and the end of the Cold War—helped bring about the disintegration of the federal state the wartime Partisan leader had almost single-handedly created. In the 1990s civil war again broke out in the Balkans, again with its characteristic viciousness: rape, torture, murder on a massive scale, with women and children not exempted.

Will it ever end? Not bloody likely.


For further reading Anthony Brandt recommends Black Lamb and Grey Falcon, by Rebecca West; Partisans and Guerrillas, by Ronald H. Bailey; and Shadows on the Mountain, by Marcia Kurapovna.

Originally published in the May 2012 issue of Military History. To subscribe, click here.