1) the launch of Tomahawk missiles from the land and sea borders, but certainly North Korea would respond immediately, by also using the approximately sixty tunnels in the territory of the South Republic and its underground military airports in the North.
2) Bombings on North Korea by Stealth aircraft which - as North Korea knows all too well - can carry nuclear warheads. Also in this case, however, the Democratic People's Republic of Korea could react by hitting the US bombers directly or by launching limited missile attacks against US installations in South Korea.
3) The US aircraft launch of some Massive Ordnance Penetrators (MOPs), the new “bunker buster” bombs penetrating and destroying tunnels, hardened targets or targets buried deep underground - an action coupled with that of the "electromagnetic railguns" that could be fired by some US ships. A Hollywood action movie scenario having two limits: the low reliability of the two new weapons and the fact that North Korea has not only hidden, but also visible bases.
Moreover, the visible bases can react to the US operations from the South or from the sea in a very short time, shorter than the duration of the US attack itself.
It is also worth noting the scarce trust the US military decision-makers have in the South Korean armed forces, never mentioned in these programs.
In North Korea, the US Presidency wants to hit mainly the structures producing and collecting nuclear weapons; the facilities to build and keep missiles; launch bases, especially the mobile ones; the nuclear submarine ports and the artillery stations near the Demilitarized Zone.
Hence let us do some accounting.
North Korea has ten major military bases; fourteen missile launch bases in addition to at least ten additional mobile bases already in operation; two bases for nuclear tests and sixty-four nuclear weapons already available.
Too many targets to enable the United States, and possibly South Korea, to carry out a limited action on the Demilitarized Line not triggering off a response at the highest level.
If the US forces’ operations are targeted they are irrelevant, while if they cause significant damage they are a real act of war.
As often repeated by Kim Jong Un, North Korea sees the US strategy in "peripheral" countries, now defined by the end of Saddam Hussein and Muammar al-Gaddafi.
Considering those examples, the North Korean leader does not trust the United States should they win a war against him.
Hence any attack on North Korea, albeit limited, would immediately trigger off the greatest possible reaction.
Furthermore, pending a US attack - also only counterforce and not counter-resource - North Korea could also attack, with conventional carriers, the South Korean areas the United States needs as bases.
Currently the US military installations in South Korea are twenty-seven, all in areas that can be hit by North Korean missiles with an acceptable degree of precision and accuracy.
According to the Western intelligence sources, with approximately sixty nuclear warheads available; a potential missile average range of 10,400 kilometres; 5,000 tons of nerve gas already stocked; 1,300 aircraft; 300 helicopters; 430 warships; 70 submarines; 4,300 tanks; 2,500 armoured vehicles and 5,500 multiple launchers, North Korea is by no means an easy opponent.
Obviously such a military build-up can safely sustain a second nuclear strike and launch a second nuclear salvo against the enemy even after a first nuclear attack from the United States and South Korea, as well as maintain sufficient conventional forces to be used after the exchange of nuclear strikes.
It is also worth adding that South Korea's central Command has claimed it suffered a cyberattack in December 2016, which means that North Korea has all South Korea’s Command plans available and, we assume, even much of the US military planning involving South Korean forces.
As maintained in a recent Workers’ Party document, the North Korean nuclear forces are not a way to get money from "imperialists".
As claimed by the North Korean single Party’s leadership, they are a way to reaffirm their independence until "imperialists" disarm their nuclear warheads "all over the world."
Reading between the lines, this is the ideological rationale of the construction of missiles capable of reaching the US territory, so as to simultaneously threaten both the US allies in Southeast Asia and Japan and the United States itself.
As already seen, the layout of bases and the amount of warheads do not permit a US "surgical" action which, however, would be interpreted as the beginning of a real war.
In 2016, North Korea carried out over 20 missile launches. Strategically this means that North Korea wants to mainly implement the intercontinental and the submarine-launched ballistic missile sectors, in particular.
This is a way to increase the likelihood threshold for nuclear or conventional attacks and to create "double deterrence", namely deterrence towards the US stations in the Pacific and on the US territory.
Furthermore Kim Jong Un is steadily in power and he is rapidly getting stronger.
Since his rise to power in 2011, the North Korean leader has "eliminated" at least seventy officials or military officers, in addition to a much larger number of them who have been "purged" according to the best traditions of Communist Parties in power.
Kim Jong Un's policy line has been designed to combine military and economic development - the policy line the Workers' Party has hoped since 2003, by supporting North Korea's entry into the "knowledge-based economy" and the expansion of "light industry".
This is the Korean translation of the Chinese model of economic reform after the Four Modernizations. It is the North Korean variation of Xi Jinping's "great reform", although the two countries are currently not in the best phase of their relations.
From a strategic viewpoint, China views for North Korea the implementation of three points, summarized in a principle that Xi Jinping plans to support with the utmost clarity and speed: "no war, no instability and no nuclear weapons" - a principle that after the 2013 tests has been reworded in the policy line of " denuclearization, peace, stability and fast resumption of the Six Party Talks".
I think that the Chinese policy is fully rational.
China does not want a strong nuclear power on its borders, even if it were a friendly country.
Certainly, North Korea is an excellent buffer State avoiding the contact between the forces of the Chinese People's Liberation Army and the US forces in South Korea - a primary strategic target.
Nevertheless if the North Korean nuclear strategy gets global and capable of making both the US territory and some Pacific countries - with which China has and wants to maintain good relations - the target of a nuclear attack, the calculation of the Chinese strategic equation on North Korea gets complex and not necessarily positive.
Moreover, the Chinese ruling class is still divided on North Korea’s denuclearization. The Chinese decision-makers fear a collapse of the regime following the denuclearization and hence a crisis that would immediately affect China's territory.
Hence it is exactly this ambiguity among the Chinese leaders which enables North Korea to keep on strengthening and upgrading its nuclear arsenal undisturbed.
Currently, however, the perceptions of the two main players, namely the United States and North Korea, are still to be changed in the light of a better understanding of both countries’ global strategy.
The United States and South Korea do not want to invade the North Korean territory.
The United States does not want new territories. It possibly wants "friendly" States not annoying it militarily, hosting their bases - and the United States already have nearly 800 bases around the world - not signing adverse commercial agreements and accepting the dollar in international transactions. Nothing else.
Or, more precisely, only the United States has no interest in following this military option.
And it is the country organizing South Korean forces.
Hence the United States has no interest in direct invasion. Indeed, the more North Korea extends its range of ICBMs, the more the United States feels threatened, in a region where it wants to maintain its hegemony. Therefore the United States can be really pushed to organize a preventive attack.
Probably said attack would end up as already described. In that case, however, two new factors should be assessed: North Korea’s comparative weakness faced with a long-range attack, which would certainly cause some serious damage, and the North Korean forces’ immediate reaction, which would not make the US attack easy.
Moreover, we must consider the reaction of the Russian Federation and China, which would surely strengthen their defences on the border with North Korea, in their maritime area, and would condemn the United States, as usual. Finally they would be strategically obliged to give again credit to North Korea’s nuclear and missile activities.
The United States must not always think that the leader of a country not accepting its hegemony is always "crazy."
It did so with Hitler, who had some psychological disorders but was not crazy - otherwise we should think that the huge German masses who followed him were mad. The same holds true for Mussolini, who had syphilis but was not crazy, as well as for all the Third World leaders who did not accept the division of the world after the Second World War.
Like it or not, Kim Jong Un's strategy makes both China and Russia enter the game. They are both interested in the denuclearization of the entire Korean peninsula - hence the United States must consider both countries’ possible moves, which do not depend on assessments regarding North Korea’s alleged "crazy" leader, but on objective analyses of the strategic interests on the field.
The first possible move could be to support Kim Jong Un and the second one - not ruling out the former one - would be a credible denial area on the sea, directed mainly against the US and South Korean operations.
Furthermore, considering Trump’s leadership problems at national level, he could seriously be tempted to carry out a military action that would set internal tensions aside and would also be the implementation, in foreign policy, of the principle "America First".
If China and Russia do not make North Korea understand that the old brinkmanship theory is now over, something irreparable will probably happen.
Furthermore the United States currently understands nothing of what happens beyond its borders. Years of "exporting democracy" and Arab Springs have not enabled the US leaders to be updated on the political, cultural and social evolutions of the countries with which they come into contact.
Therefore, although currently there are three secret communication channels between the United States and North Korea, it cannot be said that the United States can truly understand the North Korean strategic logic.
Currently Russia and China could do without North Korea. They can leverage with the United States alone and do no longer need the North Korean "dragon's snout".
This is a disadvantage for Kim Jong Un. Both powers, however, do not yet understand Trump's foreign policy and, in doubt, they could choose the most adverse variable vis-à-vis the United States
I am sure that Kim Jong Un knows this and also knows how to analyse this data.
China’s and Russia’s interest, however, is always to contain the United States in South Korea, as well as avoid military contact and, above all, prevent a denial area coming from South Korea.
Beyond this limit, both countries are no longer interested in North Korea’s nuclear power and capacity.
Hence the North Korean leader can rethink his nuclear and conventional strategy, by relating it - at least for a small part - to the Asian Heartland strategy.
Therefore the 2005 Six Party Talks should be resumed immediately.
With these fundamental policy lines and aims: a peace treaty between the two Koreas; North Korea’s denuclearization, but also partial denuclearization of South Korea, with a reduction of US forces stationed on the South Korean territory; economic and technological support to North Korea; establishment of normal diplomatic relations between North Korea, the United States and Japan; energy cooperation.