10 of the Bloodiest Battles of World War II

The battle of Okinawa was to be a precursor to the anticipated invasion for the mainland of Japan. On April 1, 1945, more than 60,000 soldiers and U.S. Marines of the 10th Army stormed ashore at Okinawa. Initially they were met with little resistance from the Japanese. But then heavy fighting broke out on the island's southern end, and a battle ensued for three months on land, sea and in air. Heavy rain and the rugged terrain made it difficult to get around and gave the Japanese easy defense positions.

The Japanese also began using devastating air attacks with kamikaze pilots who intentionally steered their planes into U.S. ships. As many as 355 Japanese kamikaze aircraft dove into Allied ships at Okinawa. The Japanese also held back on launching their major ground counterattack until U.S. troops were inland and out of range of naval support. Although the U.S. troops eventually prevailed, more than 12,000 American soldiers died in the fight there; another 49,000 Americans were injured. More than 100,000 Japanese combatants and as many as 150,000 civilians were also killed.

The invasion of Normandy, also known as D-Day or Operation Overlord, is one of the gutsiest battles of the war. It brought together the land, air and sea forces of the Allied armies June 6, 1944, to storm the beaches of German-occupied France.

The offensive actually delivered five naval assault divisions to five beaches along the shores of Normandy, France. The force included 7,000 ships and landing craft from eight Allied countries with nearly 133,000 troops from England, Canada and the United States. From the early morning hours, the Allies used air support to bomb the German troops stationed there. Although it was meant to be a surprise, German forces were prepared for an invasion and didn't go down without a fight. The fiercest fighting occurred on Omaha Beach. There the Germans were positioned on steep cliffs; as Allied troops leapt from their landing boats, they were immediately pinned down by machine-gun fire. More than 4,700 were killed or wounded on Omaha Beach that day alone. According to the National D-Day Foundation, there were nearly 10,000 Allied casualties that day, and more than 4,000 deaths.

After the invasion of Normandy, things were looking up for the Allied troops as they marched into Belgium. They hoped to find a significantly weakened Nazi defense. Unexpectedly, however, the Axis forces launched a huge counteroffensive on the Allies as they were making their way through the thick Belgian forest in the bitterly cold winter of 1944.

In December 1944, Allied air support was grounded as a result of the bad weather, and Hitler's forces seized the opportunity to strike. For a few weeks, the Nazi troops and their tiger tanks prevailed, having pushed Allied forces back several miles. The Germans seized key crossroads, and advanced toward the Meuse River, creating the plan that gave the battle its name. However, by Christmas, Patton's Third Army had relieved weary soldiers in Bastogne, and the 2nd U.S. Armored Division stopped enemy tanks short of the Meuse River as well. The tide had turned, and by mid-January, the Allies had fought their way back to their original position in the Ardennes Forest. The battle turned out to be a failed last-ditch effort on Hitler's part to regain an upper hand in the war.

It's estimated that more than 1 million Allied troops fought in the Battle of the Bulge, including 500,000 Americans. The Battle of the Bulge is considered the largest and bloodiest single battle fought during WWII. More than 19,000 U.S. soldiers died during that winter, and more than 70,000 were wounded or went missing.

On June 22, 1941, Nazi Germany launched Operation Barbarossa, Hitler's code name for invading the Soviet Union. By mid­-1942, Hitler had his eyes set on Stalingrad for two reasons. First, Stalingrad was an industrial city on the Volga River that not only produced military supplies, but also served as a key strategic hold in the invasion of Russia. Second, capturing it would secure the German army left flank as they advanced into the oil-rich Caucasus region — the goal was to cut off fuel to Stalin armies.

The Nazis first attacked the city by air, bombing the Volga River and then the city of Stalingrad, leaving much of the city in ruins. Stalin demanded workers take up fighting and women dig trenches at the front lines. On July 28, 1942, he famously declared his Order No. 227, which forbade troops from leaving the city. "Not one step backward!" he said. Those who surrendered faced military tribunal and possible execution.

German ground troops eventually marched into Stalingrad and overtook much of the city. But a relentless Soviet army held strong and fighting raged on. When the brutal Soviet winter set in, German troops were in trouble. The Soviets were choking off the supply lines and attacking them from their homes, buildings and even the sewers. But Hitler refused to surrender, even as his men starved. By early 1943, Soviet troops had captured 100,000 German soldiers and Stalingrad.

And it was a decisive battle that changed the tone of the war in favor of the Allies. Although the Soviets took back Stalingrad, it was the first public failure Hilter acknowledged. More than 1,100,000 Soviet forces, and approximately 40,000 civilians died during the battle. Axis casualties are estimated to have been around 800,000.

The Siege of Leningrad lasted nearly 900 days, from September 1941 to January 1944. As part of Operation Barbarossa, Hitler ordered a blockade around Leningrad, essentially making it inaccessible to the outside world. The blockade prevented food, fuel and all other essentials from getting to those trapped inside. During the winter of 1941 and 1942, citizens were allowed just three slices of bread a day, and many died of starvation.

As you might expect from a siege like this, the number of deaths was astronomical. Famine was the main cause of death, and while it's difficult to give exact figures, most historians agree that nearly 1 million people died during the siege. At the start of WWII, Leningrad had a population of 3 million people. Some died of disease, others froze to death though most died of starvation.

Germany's invasion of Poland is what all but started World War II. It's a "string" of many battles fought through the country to Germany's east and Russia's west. But because it was frequently difficult to discern where one battle stopped and another started, many historians lump the invasion of Poland into one great, bloody rout.

The invasion resulted after Hitler and Stalin signed the German-Soviet Nonaggression Pact, which said the two nations wouldn't fight each other. This ensured Hitler wouldn't fight the Soviets in Poland and left Germany and Russia to overrun and divide Poland.

On Sept. 1, 1939, the Germans attacked Poland from the west, and the Polish forces retreated directly into the hands of the Russians, who were waiting to attack from behind. Caught in the crossfire of this secret pact between their neighbors and awaiting aid from France and the United Kingdom that never came, 65,000 soldiers from Poland's 950,000-strong military force were killed, more than 133,000 were wounded and the rest were considered captured. Fifty-nine thousand soldiers from the USSR and Germany were killed or wounded [source: The Atlantic Monthly].

At the same time the Allies were conducting D-Day on the shores of Normandy, France, Stalin and the Soviet Union were launching another attack — this one code-named Operation Bagration in Soviet Byelorussia. The offensive lasted from June 22 to Aug. 19, 1944, and was massive; it included more than 2.3 million men. Its goal was to support the Allied operations in France and liberate Russian territory.

The offensive used massive artillery bombardment and tons of ammunition fire. Soviet bombers flew 1,000 attacks to soften up German defenses and drain morale. In just three days, five German divisions — about 28,000 men — were completely wiped out by the Soviets.

The Soviets eventually pushed German troops back to Poland, which meant they were fighting the war on the Eastern Front against the Soviets, and on the Western Front, against Britain, France and the United States. By the end of one month, Germany's Fourth Army and almost all the Ninth and Third Panzer armies were destroyed.

All told, Operation Bagration cost Hitler and the German army 350,000 men, including 31 generals. It was his worst military defeat of the war. Despite the crushing blow to Hitler, more than 765,000 Soviet troops also were killed.

The Battle for Iwo Jima began Feb. 19, 1945, when 70,000 U.S. Marines landed on the island after months of naval and air bombardment. It was immediately clear the Marines were facing a resolute and well-prepared enemy. The Japanese were dug in and hiding in the island's maze of hidden underground tunnels. The island's beach was steep and composed of shifting black sand, volcanic cinders and ash. The terrain further impeded the Marines and made it difficult to use their tracked vehicles. Men, machinery, tanks and supplies piled up at the shoreline, and were constantly barraged with artillery, mortar and machine-gun fire. Ships were also attacked by kamikaze pilots.

While the Marines reached the summit of Mount Suribachi Feb. 23, raising the U.S. flag in the iconic image we think of when we hear Iwo Jima, the battle for this small island lasted another month [source: History.net]. Of the 21,000 Japanese fighters who defended Iwo Jima, just 216 survived and were taken prisoner. More than 6,800 U.S. forces were killed and 19,217 were wounded or injured.

In the early spring of 1945, the Soviet army marched toward Berlin, where Hitler was dug in amid the ramshackle remains of his once-great Third Reich. It would be one of the last battles of WWII, and like a trapped animal, Hitler had two options: play dead or fight. Hitler chose the latter.

On April 16, Soviet troops try to encircle Berlin, Hitler readied his troops, including the Wehrmacht (defensive forces), Volkssturm (militia), Waffen-SS (elite police force), and thousands of Hitler Youth, for a desperate last stand. In all, there were 300,000 German troops. The Soviet forces, on the other hand, numbered in the millions [source: BBC].

On April 21, 1945, the Soviet shelling begins and the troops enter the city in what becomes a ground offensive. Years of Allied bombing had already left the German city of Berlin in ruins. After just a few days, the Berlin garrison surrendered to the Soviet army. That was May 2, 1945. Hitler and many of his followers committed suicide. But that wasn't before 80,000 Soviets and an estimated 300,000 Germans were dead.

In the 1930s and 1940s, British forces were stationed in Singapore. The island was still considered the gold standard for British outposts in Southeast Asia. While an attack from the Japanese during that time was considered likely, so was a victory by the British.

But in 1941 (nearly simultaneously with the Japanese attack on Pearl Harbor), the Japanese beat the British out of Malaya and then turned their sights on Singapore. The Japanese took the island by surprise and were brutal.

Despite being outnumbered more than two-to-one — there were British, Canadian, Indian and Australian forces there — the Japanese had superior air power and military intelligence. They destroyed Britain's naval and aerial capabilities before ever stepping foot on the island. On Feb. 8, 1942, 23,000 Japanese forces entered Singapore and by Feb. 15, 1942, the island had fallen. In just a week, Lt. Gen. Arthur Percival had to surrender to the Japanese commander in what is still the largest capitulation in British history.

More than 130,000 Allied troops were taken prisoner, including 15,000 Australian soldiers and 50,000 ethnic Chinese, though the numbers vary depending on the source. Many Allied troops were sent to Japanese prison camps, the vast majority of whom never made it home.