Last time we spoke about Operation Downfall. The Allies, under General Krueger, initiated a decisive campaign to clear the Japanese from Luzon. As they faced the entrenched Shobu Group, challenges included treacherous terrain and a resilient enemy. Simultaneously, Japan braced for an invasion, mobilizing reinforcements and devising defensive strategies to ward off the impending Allied assault. As July approached, General Yamashita’s forces prepared to execute a final breakout, but progress was hampered by relentless guerrilla attacks and adverse weather conditions. With Operation Downfall looming, Allied troops focused on strategic landings in Kyushu and Honshu, driven by a relentless determination to defeat the Japanese militarily. The intense battles of Luzon became a precursor to this monumental operation, marking a turning point in the Pacific War. 

This episode is The Siege of Japan

Welcome to the Pacific War Podcast Week by Week, I am your dutiful host Craig Watson. But, before we start I want to also remind you this podcast is only made possible through the efforts of Kings and Generals over at Youtube. Perhaps you want to learn more about world war two? Kings and Generals have an assortment of episodes on world war two and much more  so go give them a look over on Youtube. So please subscribe to Kings and Generals over at Youtube and to continue helping us produce this content please check out www.patreon.com/kingsandgenerals. If you are still hungry for some more history related content, over on my channel, the Pacific War Channel you can find a few videos all the way from the Opium Wars of the 1800’s until the end of the Pacific War in 1945. 

Boy I have been waiting a long time to come to this point. One of the most significant events in human history that deeply affects us to this very day. Nuclear war is as much a threat today as it was during the cold war. The dropping of the Atomic bombs on Hiroshima and Nagasaki were deeply complicated events fraught with issues of morality. It goes without saying whether or not the bombs needed to be dropped, their actual impact on the surrender of Japan and so forth are still issues hotly debated to this very day. I have spoken on the issue countless times on my personal channel and podcast, but I figure to do this subject justice I will create a full episode for it. Thus in this episode we are going to just cover what happened, but rest assured I will come back to this later on.

As we last explored, following the successful invasion of Luzon in the Philippines, along with the fall of Iwo Jima and Okinawa, American forces began preparing for the final invasion of the Japanese Home Islands. This operation was codenamed Operation Downfall. One key initiative leading up to this invasion was a comprehensive air-sea blockade and bombardment campaign against Japan itself. Previously, we detailed the extensive firebombing and precision bombing efforts executed by General LeMay’s 21st Bomber Command. However, during this crucial period, the B-29 Superfortress bombers undertook a distinct operation under the codename Starvation. This single operation would be one of the largest factors that contributed to the surrender of Japan and its one most people have never heard of.

In July 1944, Admiral Chester W. Nimitz proposed a bold plan to use B-29 Superfortress bombers to mine the waterways surrounding the Japanese Home Islands. Although Generals Henry H. Arnold and Walter Hansell expressed concerns that this mining campaign could distract from the B-29's primary role as a strategic bombardment aircraft, they eventually agreed to assign one bomber group to focus on aerial mining when conditions permitted. On December 22, Hansell's 21st Bomber Command was directed to formulate a naval mining program aimed at executing between 150 to 200 sorties each month, which was set to begin in April 1945. However, by this time, General Curtis LeMay had taken command of the 21st Bomber Command. LeMay was notably enthusiastic about the idea and successfully recommended to Washington an upgraded mining program that aimed to deploy up to 1,500 mines each month using a full B-29 wing. LeMay viewed aerial mining in a different light than Arnold or Hansell, seeing it as a vital extension of strategic bombing. He recognized that most of Japan's war production materials, as well as a significant portion of its food supplies, were imported from regions such as China, Southeast Asia, and the Dutch East Indies. Japan's industrial heartland is primarily found on Honshu, its largest and most industrialized island, while Shikoku, another island, also lacks essential resources such as iron ore and high-quality coal. These crucial materials were sourced from Kyushu and Hokkaido, both of which are other Japanese islands. All these resources were transported by sea, so without easy access to raw materials, Japan’s industrial output would come to a grinding halt. The only aircraft capable of deploying mines effectively where they were needed were the B-29s. Areas such as the Inland Sea, the Sea of Japan, and the Korean Peninsula were out of reach for other Allied aircraft. Additionally, Allied submarines could only venture into these perilous waters with great risk. Notably, about 80% of Japan's merchant fleet utilized the Shimonoseki Strait, a critical waterway that separates Kyushu from Honshu. Understanding the strategic advantage of closing this strait, LeMay decided to allocate an entire wing of B-29s specifically to mine this vital route.

Brigadier General John Davies commanded the 313th Bombardment Wing, tasked with deploying approximately 2,000 naval mines each month into Japanese waters. The primary goals of this operation were to prevent essential raw materials and food supplies from reaching the Home Islands, hinder the supply and mobilization of Japanese military forces, and disrupt transportation routes in the Inland Sea of Japan. Between March 27 and April 12, Davies’ bombers targeted key enemy shipping bases located in Kure, Sasebo, and Hiroshima. They also focused on the Shimonoseki Strait, a narrow and strategically important waterway that links the Inland Sea with the Tsushima Strait. Notably, after these attacks, this strait was successfully closed for two weeks. On May 3 and 5, the 313th Bombardment Wing laid down a total of 1,422 mines in the waters surrounding the Shimonoseki Strait, as well as near major urban centers like Tokyo, Nagoya, Kobe, and Osaka. These efforts aimed to severely disrupt maritime commerce between Japan’s major industrial areas. Just a week later, the minefields expanded from the Shimonoseki Strait to include Kyushu, the southernmost of Japan’s four main islands, and northwest Honshu, the largest island containing Tokyo. By the end of that month, these mines were proving remarkably effective, accounting for the sinking of more ships than Japanese submarines. In fact, within the Shimonoseki Strait alone, 113 ships had been sunk.

Between June 7 and July 8, American forces expanded and fortified minefields along the western coast of Japan while also replenishing the existing minefields in the Shimonoseki Strait and the Inland Sea. During this effort, they successfully laid a total of 3,542 mines across 14 missions. The "total blockade" officially commenced on July 9 and continued until the end of the war. Throughout this period, American forces executed 474 sorties, dropping another 3,746 mines that replenished existing minefields and extended coverage to harbors in Korea. In total, Brigadier General Davies conducted 46 missions that laid down 26 minefields containing 12,135 mines. Remarkably, only 15 B-29s were lost during these operations. In turn, the mines accounted for the sinking or damaging of 670 Japanese ships, with a total loss of 1.25 million tons. This mining campaign effectively strangled Japanese industry, as the denial of essential raw materials to factories proved more disruptive than the direct bombing of the plants themselves. 

Despite the clear vulnerability of Japan’s economy to disruptions in coastal shipping, Japanese authorities were alarmingly unprepared to address the threat posed by air-dropped mines. By August 1945, Japan had committed 349 ships and 20,000 personnel to counter the Starvation campaign, but these efforts were overwhelmingly ineffective. The shipping crisis escalated to such a degree that searchlights and anti-aircraft batteries were redeployed from urban centers to defend expected mining targets. Additionally, suicide boats were employed in desperate attempts to clear the minefields. Royal Navy historian S.W. Roskill commented on the situation, stating, “The blockade had, in fact, been far more successful than we realized at the time. Although submarines initially played a critical role in enforcing the blockade, it was the air-laid mines that ultimately strangled Japan.” Japanese officials shared this assessment. A director from a Tokyo steel company reflected on the situation, noting that the denial of essential raw materials to factories caused far greater disruption than the direct bombing of the plants themselves. This contradicted the views of US Army Air Forces experts back in Washington. In a striking remark after the war, a Japanese minesweeping officer told American forces, “The result of B-29 mining was so effective against shipping that it eventually starved the country. You could have likely shortened the war by starting this campaign earlier.”

Meanwhile, General LeMay continued his firebombing campaign against Japan. By the end of May, urban areas around Tokyo Bay had been devastated, prompting the 21st Bomber Command to shift focus westward toward the densely populated industrial complexes lining Osaka Bay. On June 1, 521 B-29s were dispatched to bomb industrial targets situated along the Yodo River, with an escort of 148 P-51 fighters. Unfor