Covert efforts are in place to counter North Korean threat
Leadership assassination and infected microchips among riskier ploys targeting regime
Japan, South Korea and China are ramping up military capabilities and devising increasingly risky and unconventional plans to counter the growing threat from North Korea.
Pyongyang fired a ballistic missile over Japan earlier this week, causing alarm across the world and deep reflection from its neighbours on whether they are prepared to cope with a clash of arms.
A military response to the North would involve rapid pre-emptive strikes, the targeted assassination of leaders in Pyongyang and defensive measures to minimise casualties.
Covert efforts to bring down the regime would include instigating internal dissent and attempts to sabotage North Korean weapons.
A decision by Washington earlier this year to station the Gray Eagle attack drone, capable of carrying four Hellfire air-to-surface missiles, at the Kunsan Air Base near Seoul by 2018 fuelled speculation that the US could target the North Korean leadership during a military escalation.
Kim Jong-un, the North Korean leader, was reported this week to have hired 10 former KGB agents to train his bodyguards as he fears assassination.
Seoul, meanwhile, is reported to be accelerating its own "kill chain" pre-emptive strike capabilities, which would use satellite reconnaissance to identify when and where North Korea is manufacturing missiles and nuclear warheads, to destroy them before they become operational.
Covert methods aimed at bringing down the regime include attaching short-wave radios to balloons and sending them across the border.
Officials in Pyongyang worry that broadcasts revealing how comfortable life is in the South could create unrest.
The United States is also rumoured to be carrying out "left of launch" attacks against the North Korean missiles - in which it deliberately allows infected microchips and other components to be smuggled into the reclusive state to be used for its weapons programme.
When the defective parts are fitted into weapons, the US is said to have the ability to send them off course or destroy them.
Defence officials in Japan - where citizens awoke to wailing sirens and were told to take cover after the launch of the missile on Tuesday -sought to allay their citizens' fears with a request for a record Y5.26 trillion (€44bn) defence budget in 2018 - an increase of 2.5pc on 2017.
The details of the budget were under discussion long before North Korea's most recent provocation, but the inability of the Japanese military to intercept the Hwasong-12 missile has added new emphasis to its security needs.
China, meanwhile, has established a brigade on its border with North Korea, where 24-hour surveillance is carried out.
Nuclear bunkers for civilians have also reportedly been built.
Wei Dongxu, a military expert in Beijing, said: "I don't think there is much chance China will send troops into North Korea or help North Korea to stop invading US troops."