President Donald Trump has been exercising his foreign–policy powers in recent weeks, with tensions escalating between the U.S. and Syria as well as the U.S. and North Korea.

In addition to approving a missile airstrike on a Syrian air base April 7 and dropping the largest non-nuclear bomb on Afghanistan on April 13, Trump sent a fleet of navy ships toward the Korean Peninsula April 8, complete with an aircraft carrier, two destroyers and a cruiser. In response to the action, a North Korean foreign minister said the U.S.’s recent attack on Syria justifies North Korea’s nuclear defense program.

The North Korean government began building up its military and nuclear defense program starting in the 1990s, with then-leader Kim Jong Il’s promoting a “military first” strategy. The intended goal of building up this immense nuclear program, as many foreign–policy analysts believe, is to ensure the country is prepared for possible war with the U.S. The U.S. currently has about 30,000 American troops stationed in neighboring South Korea, with frequent American military exercises’ occurring in the surrounding area.

North Korea has been accelerating its nuclear and missile tests in the past few years, exacerbating tensions between the country and the U.S. The country’s most recent missile test took place April 16, in which the missile exploded seconds after the launch. These recent tests have prompted members of the Trump administration to quickly condemn the country.

In a visit to Seoul, South Korea, on April 17, Vice President Mike Pence warned North Korea not to test the U.S. Mentioning the U.S.’s recent attacks in Syria and Afghanistan, Pence said, “North Korea would do well not to test his resolve or the strength of the armed forces of the United States in this region.” At the same time, the vice president did not rule out the possibilities of negotiating with North Korea “through peaceable means.” Rex Tillerson, U.S. Secretary of State, said last month that pre-emptive military action was on the table.

The U.S. has also allied itself with South Korea and China in an attempt to influence North Korea to stop its nuclear missile tests. China has recently called on North Korea to stop its nuclear tests and supported negotiations.

Despite these warnings from the U.S., North Korean officials have not shown any signs of stepping back from their nuclear tests. In an interview with a BBC reporter, Han Song-Ryol, North Korean vice foreign minister, said the country will continue conducting missile tests on a weekly, monthly and yearly basis. He also added that an “all-out war” would result if the U.S. took military action against the country.

On April 18, it was found out that the ships supposedly headed to the Korean peninsula April 8 were actually sailing toward the Indian Ocean, away from North Korea. Now, however, the naval fleet is sailing toward the Korean peninsula and is expected to arrive in the next week, White House officials have said.