• The US considered invading Japanese-occupied Taiwan in World War II.
• Top US commanders decided it would be a high-casualty nightmare.
• Today’s Chinese invaders may face similar challenges.

The United States once planned an invasion and seizure of Taiwan that would have been just as large D-day.

Operation Causeway would send hundreds of thousands of troops, supported by thousands of ships and planes, to storm the beaches of Japanese-occupied territory in 1945.

“Almost certainly, the invasion would have been a horrifying spectacle and a nightmarish ordeal,” said Ian Easton, an analyst who wrote a new paper. study on the invasion for the China Institute of Maritime Studies. “Worse than any battle that was actually fought in the Pacific. The campaign would have been prolonged and would have lasted six months or even a year.”

The CMSI study makes clear that an American invasion of Taiwan in 1945—or a Chinese invasion today—would be difficult and risky.

As many years ago, Taiwan today would likely use Japanese fortifications and tactics to defeat a large Chinese amphibious assault—illustrating the risks and dangers of any attempt to occupy the island that Beijing. views as a breakaway province.

“A Long, Long Struggle”

The genesis of the planned American invasion—eventually code-named Operation Causeway—began in the late 1920s, when the US Navy and Army strategized for a potential war with Japan. The Orange War Plan called for an advance across the Pacific, culminating in an assault on Taiwan – then called Formosa – which the Japanese Empire. annexed from China in 1895 after the First Sino-Japanese War. The plan called for 90,000 Army and Navy personnel to capture Taiwan, which would turn the island into a staging post for an invasion of Japan. By the 1930s, Taiwan had been abandoned in favor of rule over Okinawa, a smaller objective closer to Japan’s four largest islands.

In 1944, with the collapse of Japan and an invasion of the Japanese mainland looking likely, American planners again looked to Taiwan as an amphibious emplacement and a base for the B-29 Superfortress strategic bombers. adm. Navy Chief Ernest King favored the Taiwan option, while General Douglas MacArthur lobbied for an invasion of the Philippines. For a time, “General MacArthur’s return to the Philippines was viewed as a secondary and supporting campaign,” the CMSI study said.

Initial plans called for an assault of 12 divisions in early 1945. But, with the European theater receiving priority for American forces, this was reduced to six divisions (roughly the size of the initial assault force in the Normandy invasion). The objective would be to occupy southern Taiwan and the mainland Chinese port of Xiamen across the Taiwan Strait.

But that meant subduing a heavily defended 14,000-square-mile island studded with cities, mountains, and forests. The more they studied the challenges, the more concerned some senior officers became. Just finding enough forces would be a nightmare. “In all, it was believed that a force of 776,913 would be required for the Causeway, including all six US Marine Corps divisions, 20 B-29 bomber groups, 41 miscellaneous bomber squadrons, 40 fighter squadrons, and a large number of naval engineers. and logistics support units,” the CMSI report explains.

The biggest flaw of Operation Causeway was the underestimation of Japanese defenses. Intelligence estimates called for a garrison of 90,000 to 170,000 troops. In fact, the Japanese had 275,000 troops, incl native Taiwanese enlisted. They were supported by 20 squadrons of kamikaze planes and 600 suicide boats.

The Japanese had anticipated that the landings would take place in southern Taiwan. They planted 10,000 sea mines, 5,200 of them in the Taiwan Strait alone. Aware of overwhelming American firepower, they built elaborate systems of trenches, bunkers, and tunnels above the beaches and across the island.

“Imperial Japanese and Formosan troops would have fought a long, drawn-out battle in the cities and mountains,” Easton said. “A guerilla warfare campaign was planned after conventional fighting had ended. Taiwan’s defenders were determined to fight to the end, and their defensive geography, stocks, and underground bunkers were extraordinary.”

How would an American invasion of Taiwan go? Other battles of the Pacific War offer grim clues. When American troops landed in the Philippines in October 1944, they marched through jungles and mountains in a campaign that had not yet ended when Japan surrendered in August 1945. In April 1945. invasion on the island of Okinawa, American forces suffered 50,000 casualties in two months as they faced dense fortifications on hilly terrain, as well as 2,000 kamikaze attacks that sank or damaged hundreds of Navy ships.

Ultimately, the idea of ​​Taiwan was abandoned. “Militarily, it was absolutely the right decision,” Easton said. “Professional war planners loathed the idea of ​​having to fight on Taiwan, and with good reason.”

Lessons for China

Even eight decades after the end of the Japanese occupation, the Taiwanese military is still influenced by Japanese doctrine, such as the importance of strengthening air bases and how to face an amphibious invader armed with massive air and naval firepower.

Taiwanese forces still use Japanese-built facilities, including some bunker complexes. Some Taiwanese officers advocate renovating the old beach defenses and preparing for protracted guerrilla warfare, as the Japanese did.

China would face these challenges even more in an attempt to occupy Taiwan today.

“Taiwanese military officers pay special attention to history and especially the history of island warfare, urban warfare and amphibious warfare,” Easton said. “They have all the defensive benefits that the Imperial Japanese enjoyed and more, thanks to modern weaponry and strong American support.”

Michael Peck is a defense writer whose work has appeared in Forbes, Defense News, Foreign Policy magazine, and other publications. He holds a master’s degree in political science from Rutgers Univ. Follow him further Twitter and LinkedIn.