Kim Jong Un looked on last Friday as North Korea fired a short-range missile off its east coast. This event is the latest in a series of North Korean missile launches in response to what the media has called an extended period of elevated military tension on the Korean peninsula, triggered by Pyongyang’s fourth nuclear test on January 6.

Friday’s launch came in the middle of the two-day Nuclear Security Summit in Washington D.C., where President Obama had hoped to meet with South Korean President Park Geun-hye and Japanese Prime Minister Shinzo Abe to “discuss common responses to the threat posed by North Korea and to advance areas of trilateral security cooperation in the region and globally.”

The U.S. has been particularly eager to encourage better relationships between its two biggest allies, as well as China, because it fears that in the absence of unilateral action, North Korea will continue to grow, and eventually use, its weapons stockpile.

North Korea has already devoted considerable resources to building nuclear weapons, about 10 to 16 warheads, and is working on an intercontinental ballistic missile for delivering them. If it succeeds, North Korea will be the first country this century to develop nuclear weapons with the capability to reach the United States. Major cities including New York and Washington are particularly at risk.

Last Saturday, the North Korean state media released a propaganda film titled “Last Chance,” showing a submarine-launched nuclear missile destroying the Capitol building. This film comes on the heels of strict economic sanctions, similar to those recently lifted in Iran, that the United States placed on North Korea following their nuclear test in January.

The UN also imposed the strongest sanctions on North Korea in over two decades. The UN resolution instructs countries to inspect all cargo to and from North Korea, cut off shipments of aircraft and rocket fuel, ban all weapons sales and restrict all revenues to the government unless for humanitarian purposes.

Countries are also required to expel North Korean diplomats affiliated with illicit programs and to honor the long list of sanctioned individuals and entities. According to Adam Szubin, the Treasury’s top sanctions official, the U.S. “will work closely with our international partners to continue in a strong and unambiguous way to pressure North Korea to abandon its illicit nuclear and ballistic missile programs.”

In recent weeks, Pyongyang has also upped the rhetorical ante with daily threats of nuclear and conventional strikes against South Korea and the U.S. mainland in response to large-scale South Korea-U.S. war games. In a statement issued on Monday, the North Korean National Defense Commission affirmed that it would take a “pre-emptive and offensive nuclear strike” in response to the exercises.

The statement additionally said that North Korea has “a military operation plan … to liberate South Korea and strike the U.S. mainland ratified by our dignified supreme headquarters.”

This year’s annual spring exercises in South Korea are some of the biggest ever, involving 17,000 U.S. troops and around 300,000

South Korean troops. The goal of these exercises is to ensure readiness for any North Korean attack through a combination of battlefield and computer-simulated exercises.

Preparation for nuclear proliferation has taken precedence as officials are even more conscious of the threat that North Korea poses to major American cities following the terrorist attacks in Paris and Brussels. They fear that North Korea will aid ISIS and other terror groups in obtaining nuclear material or other radiological material needed to make a dirty bomb. If detonated, the blast from these weapons can kill thousands and spread cancer-causing substances over a vast area, triggering panic and evacuations.

“Even if it is small, such an incident would create such havoc in the world that you have to take it quite seriously,” said former Ambassador Wendy Sherman, who spearheaded U.S. nuclear negotiations with Iran and North Korea.

A dirty bomb detonated in a major city could cause tens of billions of dollars in economic damage. People and businesses would have to be relocated while the contamination is cleaned up, and few would be inclined ever to go back.

The growing threat of nuclear proliferation has caused many Americans to question whether or not we should build up our own weapons stores. While increasing the stock of such weapons may increase our security in the short run, it could lead to an arms race with North Korea similar the one that occurred during the Cold War.

Instead of starting an arms race, President Obama hopes to approach the North Korea question through non-violent means, namely by working with regional powers to cripple North Korea’s economy. In the meantime, officials should continue to monitor the situation closely and prepare for the possibility of mobilization and violence.