The war of words between the US and North Korea is being watched all over the world, but of all the nations purportedly without a horse in the race, it may be Iran that is the most interested. With diplomatic engagement between the US and Iran recently restored and moderate Prime Minister Hasan Rouhani back in power, many believe that Iran is setting a new, less confrontational path, content with its current nuclear programme and it’s empowered position in the Middle East.

However, Iran is not about to stop climbing the greasy pole to international supremacy. That’s why Iran is keeping a close eye on how President Trump deals with North Korea. Co-operation between Iran and North Korea began in earnest during the 1980s, when Iran supplied oil to Kim Il-Sung’s regime in return for military equipment it needed for the Iran-Iraq war — despite the obvious ideological differences of their respective leaders. Forming part of George W. Bush’s “Axis of Evil,” North Korea was often used as a conduit for arms deals between the Communist Bloc and Iran, before the nation began to produce and sell internally made weapons, and the nations now co-operate to develop military technology. Although the exact relationship between the two is unknown, what is clear is that North Korea continues to provide missile technology to Iran — and possibly technology with the capability to create fissile nuclear material.

So apart from seeing if their missiles work,  should the worst happen, why is Iran so interested in the new administration’s handling of North Korea?

The first reason is simple. Iran is aware that North Korea’s challenge to the US tests Trump without putting anything of theirs on the line. Should Trump’s words prove to be nothing more than that, Iran will know it has room to manoeuvre. It can wilfully ignore Trump’s warnings about destabilizing the region, expand the support it gives to allies such as Hezbollah and seize on new opportunities (as it has done in Yemen) with impunity. Should Trump choose to make good on his threats to the Kim regime, however, Iran will know it is not dealing with the blustery, clueless caricature that has been portrayed in the media, but rather a serious international statesman who is keen to reverse America’s withdrawal under Obama. For Iran to be offered such a chance, without risking anything significantly of its own, is an opportunity it simply cannot pass up.

However, Iran will also see great benefit in the US being forced to turn its focus away from the Middle East. Iran can use this breathing room to make hay in the Middle East. It can continue to support militias to ensure an influential role in a post-ISIS Iraq, expand support to Hezbollah or fund new rebel groups — all whilst flying under the radar as the eyes of America’s security community are fixated elsewhere. Iran could soon sows the seeds of discord in a number of states, creating an arc of instability around suddenly isolated US allies such as Saudi Arabia and Israel. It may also use this opportunity to finally cement its “road to the sea” as more than just an idea, but as a concrete reality.

Should North Korea successfully develop ICBMs, then Iran stands to benefit greatly from proliferation. North Korea’s nuclear and missile technology will inevitably migrate from the Democratic People’s Republic of Korea to the Iran. The Islamic Republic can trade oil, of which it has plenty, but, rather than receive hard cash, of which North Korea has little, it will receive missile and nuclear technology.

So to US interests, the North Korean escalation matters not just in Asia, but in the Middle East. Iran could exploit a regional disturbance — albeit a truly significant one — and turn it into a major challenge to the US and allied strategic interests.