North Korea is signaling this will be its busiest year of missile testing yet. In March, the regime conducted nine tests, the most in a single month recorded in our database.

Recall that on April 21, 2018, Kim Jong Un declared North Korea would cease intercontinental ballistic missile and nuclear tests in the lead-up to a summit with U.S. President Donald Trump. However, Kim’s stated reason for the pause — more pragmatic than diplomatic — asserted it was because North Korea had “completed its mission” for its nuclear and missile program.

As diplomatic talks stalled, North Korea slowly began to unwind its pledge, and in May 2019, over a year after initially pledging to halt tests, it resumed launching missiles. Finally, on Jan. 1, 2020, Kim stated he no longer felt “unilaterally bound” by North Korea’s moratorium on long-range missile and nuclear tests.

These renewed tests had a few different characteristics: They were smaller, of shorter range, solid-fueled and new. Their novelty is especially important: Remember, Kim’s stated reason for the testing freeze was because he felt confident enough in the systems he had already tested so as to make future tests of them superfluous.

That the missiles tested since May 2019 have been entirely new is not a coincidence and is perfectly in line with Kim’s stated logic for the initial freeze. Several of North Korea’s new missiles were so new, in fact, they had never been seen by analysts in the open-source sphere. The regime needed to test the newer systems to verify that they worked. Even more surprising, the tests appeared to have been largely successful.

As of writing, North Korea has conducted at least 35 missile tests, only one of which appears to have failed in flight, since resuming tests in May 2019. Even if there were a few more failed flight tests that North Korea had successfully covered up, this is a remarkable feat. It demonstrates that, while North Korea spent over a year not carrying out missile tests, it continued missile development.

There is zero reason we should assume North Korea has limited its research and development activities to its short-range systems. Given that these tests have all been of solid-fuel missiles, and that North Korea has already successfully tested and fielded longer-range, solid-fuel systems before its self-imposed testing freeze, the regime is likely working to expand its solid-fuel missile capabilities to achieve an intermediate-range capability, and potentially intercontinental range.

Currently, North Korea’s intermediate-range ballistic missiles and ICBMs are all liquid-fueled systems, which are fragile and can only be fueled right before flight, costing precious time in a potential conflict. If North Korea is working to expand its solid-fuel capabilities into longer-range systems, it is likely the regime would want to test those weapons as well.

There are a few statements from the regime corroborating this. Most notably, following the March 21 test, North Korea explicitly stated that “the tactical and strategic weapons systems in the development stage will make decisive contributions” to North Korea’s strategic plan and reworked defense strategy. These systems will need to be tested in order for North Korea to be confident in them.

Finally, we are moving into what is historically the most active testing window for North Korea. Individual tests might not be possible to predict, but on the whole, North Korea’s testing activities follow a somewhat regular pattern, with tests beginning in late February or early March and then proceeding through mid-September before dropping off for the year.

The graphic below shows North Korea’s cumulative tests throughout the year starting in 2012.

This graph illustrate that, while March is historically the most active month for North Korean missile tests, we are far from out of the woods when it comes to North Korea’s missile testing season.

There’s been speculation that North Korea’s March 2020 tests were an attempt to demonstrate the regime is unaffected by the new coronavirus pandemic ravaging the rest of the world. While that could have played a part in it, and while we cannot know for sure, I believe we would have seen a similar number of missiles launched even without the pandemic.

This leaves U.S. policy and the chances for diplomacy with a dismal outlook. As with two years ago, when North Korea was preparing to meet the president for a summit, North Korea will not voluntarily give up its nuclear weapons or missile systems. The best that negotiations can probably hope to gain is to restart and lock in North Korea’s missile and nuclear-testing moratorium in exchange for some sanctions relief.

My colleagues have written in depth about what the specifics of that might look like. While hardly the U.S.’ most preferred outcome, it would at least ensure the regime would be limited in furthering its ability to strike the U.S. Potentially, in time, North Korea’s current capability may even decay if it is unable to carry out tests verifying its systems function as expected. If not, then we may once again look back to now in a year’s time as another missed chance to slow North Korea’s missile development.

Shea Cotton is a research associate at the James Martin Center for Nonproliferation Studies at the Middlebury Institute of International Studies. He created and manages the North Korea Missile Test Database of the Nuclear Threat Initiative, as well as the Global Incidents and Trafficking Database.