South Korea is spending a record $42.4 billion on defense in 2022, 4.5 percent more than 2021. Nearby (separated by the 65 kilometer wide Tsushima Strait) Japan is also spending more in 2022, a record $50 billion, which is four percent more than 2021. Japan has a larger navy and air force than South Korea but both nations build or buy similar ships and aircraft. Japan has had hostile relationships with both Koreas since World War II because of four decades of brutal occupation by Japan and attempts to make Korea a part of Japan. Even before that Korea and Japan had a long hate-hate relationship. The occupation just made it a lot worse. Yet North Korea has been hostile to South Korea since World War II and as North Korea developed ballistic missiles and nuclear weapons, South Korea and Japan tried, with mixed success, to reduce their mutual hostility over the occupation and much else.
Meanwhile North Korea and China consider the combined military capabilities of Japan and South Korea as a single threat to Chinese domination of East Asia. The combined defense spending of South Korea and Japan is more than ten times what North Korea spends but only about a third of Chinese defense spending. What threatens Chinese military domination the most is the quality and quantity of the South Korean and Japanese air and naval power. Both nations are buying F-35 fighters and building their own submarines and aircraft carriers. Combine this with the military forces of other nations confronting Chinese aggression and expansion, a coalition that now includes India, Vietnam, Singapore, Indonesia, Malaysia, Taiwan and American forces in the West Pacific, and you get a better idea of the Chinese predicament.
South Korea has a larger army than Japan because South Korea has to face the possibility of a land invasion by North Korea. South Korea also has a large and modern air force, including F-35s. Currently South Korea is buying at least 40 F-35s while also developing a modern jet fighter, the KF-21 for itself (about 120) and export. Many of the F-35s are needed for the DDH type (helicopter carrier) ships that can operate F-35Bs.
North Korea considers all these F-35 purchases a hostile act and direct threat to them. That about sums it up. In the event of a war, the U.S. plans to bring in over 200 more air force and navy F-35s for use against North Korea or China, depending on who is the aggressor.
South Korea and Japan are also building Aegis destroyers and more AIP powered submarines. Both Japan and South Korea are beginning to use lithium-ion batteries on subs, which are superior to current submarine batteries. Japan pioneered the use of lithium-ion batteries for submarines.
During the last decade, as North Korean and Chinese military threats became more obvious, Japan and South Korea have been increasing defense spending each year. North Korea openly complains about how unfair and unfriendly these increases are, but they are a direct result of the increasing threat from North Korea. Both Japan and South Korea each have annual defense spending that is more than a third larger than the annual GDP of North Korea. That is one reason North Korea spends about a third of GDP on defense compared to 1.2 percent for Japan and nearly three percent for South Korea.
The disparity in military manpower is also unusual. While North Korea has a nearly a million men (and some women) in its military, South Korea has 500,000 and Japan 247,000. While North Korea depends on a large number of poorly equipped troops, Japan and South Korea depend a lot more on high-tech weapons, and lots of them, plus lots of training for the all-volunteer Japanese force and South Korea’s mostly conscript forces, which are trying to achieve all-volunteer status. A growing portion of the South Korean defense spending is going to improve the pay and living conditions of its career military personnel and conscripts. This, the South Koreans discovered, was one of the best ways to increase the number of conscripts accepting offers to make the military a career. If not, the improved morale improves the quality of the military reserves. It’s the voters in both countries that are calling for more defense spending and improving the quality of the armed forces.
North Korea spends a disproportionate amount of its defense budget on ballistic missiles and trying to perfect nuclear weapons. Since Japan is an island, its army has only 150,000 troops. The structure of the Japanese army is also unique. It has nine divisions; eight infantry and one armored. There are eight independent combat brigades; five infantry, one airborne, one airmobile and one amphibious. The divisions are relatively small with 6,000 to 9,000 troops each while the brigades have 3,000-4,000 troops each. These brigades and divisions are heavy on firepower. All the infantry divisions and brigades are basically local defense units. The divisions have only three infantry battalions with artillery and other support units typical in larger Western infantry divisions. One of those three infantry battalions is usually mechanized and acts as a mobile reserve. These Japanese divisions depend on a lot of artillery and air defense weapons plus excellent communications. The brigades are basically divisions without most of the support units. The airborne, airmobile and amphibious brigades are mobile reserve forces. Another reserve force unit is an armored division with 6,500 troops, 230 tanks and 350 IFVs (Infantry Fighting Vehicles) for its one infantry battalion and many of the support troops.
The Japanese navy and air force each have about 50,000 personnel with world-class ships, aircraft and other weapons. Most of the defense budget goes to equipping and maintaining these ships, aircraft and missile systems. The first line of defense is the fleet and air force. While the air force has 760 aircraft, the navy has 346, in addition to 154 ships. The air force is usually the first responder when any potentially hostile ships or aircraft come near any of the islands. The navy has a lot of combat ships, all of modern design. These include 37 destroyers, seven equipped with the Aegis air defense system that can also intercept ballistic missiles. Another Aegis destroyer will enter service in 2021 and two more are on order. There are also four “helicopter destroyers” that look like small aircraft carriers, which is what they are. The post-World War II Japanese constitution prohibits Japan from having aircraft carriers but the “helicopter destroyers” are being modified to use the vertical takeoff F-35B stealth fighter. Japan is making a big investment in these aircraft, with 147 in service or on order. Most (105) will be the land-based F-35A model but 42 will be F-35Bs, the version that can operate from carriers.
Ordering some F-35Bs makes it clear that Japan is going to experiment with some of these aircraft aboard the existing Japanese “helicopter carriers”. Since 2017 Japan has had operational two 27,000 ton “destroyers” (DDH type ships) that look exactly like an aircraft carrier. These Izumo class ships can carry up to 28 helicopters or up to ten vertical takeoff aircraft. The carriers are armed only with two 20mm Phalanx anti-missile cannons and a launcher with sixteen ESSM missiles for anti-missile defense. The DDH have powerful engines capable of destroyer-like speeds of over fifty-four kilometers an hour. There are also more medical facilities than one would expect for a ship of this size. Izumo does have considerable cargo capacity which is intended for moving disaster relief supplies quickly to where they are needed. Apparently, some of these cargo spaces can be converted to berthing spaces for troops, disaster relief personnel, or people rescued from disasters, as well as additional weapons and equipment needed to support F-35B fighter-bombers. Izumo can carry and operate at least ten of the vertical take-off F-35B stealth fighters now that modifications were made to the flight deck to handle the extremely high temperatures the F-35B generates when taking off or landing vertically, like a helicopter. When the first DDH entered service in 2015 Japan made no mention of buying F-35Bs or modifying the LPH flight decks to handle the F-35B. The Izumos already have an elevator (to the hangar deck under the flight deck) powerful enough to carry an F-35B fighter.
The air force handles the long-range air-defense systems, including Patriot batteries. Japan is developing more powerful air defense systems as well as new electronic warfare weapons. This includes some innovative jamming systems.
Japan’s submarine force comprises 18 very quiet and lethal diesel-electric boats, most with AIP (air-independent propulsion) that allows submerged operations lasting several weeks. This submarine force is being expanded to 22 boats.
There are 16 smaller (frigate and corvette) surface warships plus 30 minesweepers, three landing ships and lots of support ships.
The air force has 300 modern fighters, with the older ones being upgraded or replaced with F-35s. There are 13 AWACS (aerial radar and air control) aircraft, five intelligence collection aircraft and about 70 two and four-engine transports. The air force also has about fifty helicopters.
The army has about 490 aircraft, most of them helicopters. There are 17 V-22 vertical takeoff and landing transports on order.
The Japanese navy has 346 aircraft, 145 of them helicopters with most of those serving on ships. The fixed wing aircraft include 42 F-35Bs on order as well as about a hundred maritime patrol aircraft with the rest being transports and trainers.
South Korean forces long concentrated spending on the army, and buying modern weapons made in South Korea. That worked and now South Korea builds its own tanks and other armored vehicles similar, and sometimes superior, to what the United States has. South Korea ground forces are organized like the Americans and the U.S. still plans to send major ground combat units to South Korea if there is another war with North Korea or attack by China.
As a major commercial ship builder it was easy for South Korea to start building their own warships. Unlike Japan, whose post World War II constitution prohibited exporting weapons, South Korea became a major exporter of modern warships as well as combat vehicles and eventually military aircraft. This was one reason why Japan finally amended its constitution to allow military exports.
American, South Korean and Japanese forces still train together and war plans of all three countries are kept in sync so that wartime joint operations will happen without a lot of embarrassing incompatibilities or misunderstandings.