The United States and South Korea are preparing to begin their biggest combined military training in years after North Korea ramped up weapons tests and threats of nuclear conflict against Seoul and Washington.

The allies’ summertime drills will take place from August 22 to September 1 in South Korea under the name Ulchi Freedom Shield.

They will include field exercises involving aircraft, warships, tanks and potentially tens of thousands of troops.

The drills underscore Washington and Seoul’s commitment to restore large-scale training after they cancelled some of their regular drills and downsized others to computer simulations in recent years to create space for diplomacy with Pyongyang and because of Covid-19 concerns.

The US Department of Defence also said the US, South Korean and Japanese navies took part in missile warning and ballistic missile search and tracking exercises off the coast of Hawaii from August 8 to 14, which it said was aimed at furthering trilateral cooperation in face of North Korean challenges.

While the United States and South Korea describe their exercises as defensive, Ulchi Freedom Shield is expected to draw an angry reaction from North Korea, which describes all allied trainings as invasion rehearsals and has used them to justify its nuclear weapons and missiles development.

Before they were downsized, the US and South Korea held major joint exercises every spring and summer in South Korea. The spring ones had been highlighted by live-fire drills involving a broad range of land, air and sea assets and usually involved around 10,000 American and 200,000 Korean troops.

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Protesters wearing masks of US President Joe Biden and South Korean President Yoon Suk Yeol stage a rally to oppose planned joint military exercises (Ahn Young-joon/AP/PA)

Officials at Seoul’s Defence Ministry and its Joint Chiefs of Staff did not comment on the number of US and South Korean troops that would be participating in Ulchi Freedom Guardian Shield.

The allies will train for drone attacks and other new warfare developments shown during Russia’s war on Ukraine and practice joint military-civilian responses to attacks on seaports, airports and major industrial facilities.

“The biggest meaning of (Ulchi Freedom Shield) is that it normalises the South Korea-US combined exercises and field training, (contributing) to the rebuilding of the South Korea-US alliance and the combined defence posture,” said Moon Hong-sik, from the South Korea Defence Ministry.

Some experts say North Korea may use the drills as an excuse to stir up tensions.

The North has already warned of a “deadly” retaliation against South Korea over its Covid-19 outbreak it claims was caused by anti-Pyongyang propaganda leaflets and other objects flown across the border by balloons launched by southern activists.

South Korea and US officials say North Korea is also gearing up for its first nuclear test since September 2017, when it claimed to have developed a thermonuclear warhead to fit on its intercontinental ballistic missiles.