They aren’t just some high-tech toy bought off the shelf. This was a military weapon being used on U.S. Air Force pilots.

Apparently Chinese soldiers attacked U.S. Air Force pilots in Africa with laser beams last week. U.S. pilots in Djibouti said lasers struck their plane while in flight, The Wall Street Journal reported. They also said the lasers appeared to be coming from the direction of a nearby Chinese military base.

The two airmen reported symptoms of dizziness and seeing rings. (Pointing lasers at aircraft is extremely dangerous. It can temporarily blind pilots, and in the United States it’s a federal offense.) While the pilots are expected to make a full recovery, the incident raises questions about how far the United States will allow China to push it without pushing back.

But first let’s back up. What’s everyone doing in Djibouti, a tiny country in eastern Africa? America has a base in Djibouti because of its proximity to Yemen, a terrorist incubator. The 4,000 U.S. troops stationed there are tasked with conducting counterterrorism operations in the region.

What about China? Well, that’s a little more opaque. China opened its Djibouti base last August, claiming that its purpose is to help with anti-piracy patrols and other peacekeeping missions. It’s supposedly a logistics base, but here’s the thing: China doesn’t have foreign military bases anywhere in the world — except in Djibouti, eight miles from the U.S. base.

Now, back to those lasers. First, the lasers that were used to target U.S. planes are military-grade. They aren’t just some high-tech toy bought off the shelf. This was a military weapon that was being used on U.S. Air Force pilots.

Second, last week’s incident isn’t the first time this kind of thing has happened. According to The Wall Street Journal’s military sources, there have been three previous incidents involving military-grade lasers in Djibouti in the last few weeks. There was also a fourth incident that didn’t involve lasers, but no further details were given. But last week’s laser attack was the only one that caused the U.S. government to lodge a formal diplomatic complaint with the Chinese government.

So why didn’t America say something sooner? A spokeswoman for the Defense Department said that a complaint was lodged this time because of the injuries sustained by the airmen and because the latest attack indicates that the frequency of these incidents is on the rise.

But it also sounds like that fact has been known for some time. The U.S. military was concerned enough about the risk of these laser attacks that it had previously warned pilots to use caution when flying over certain parts of Djibouti. And while such laser attacks have only just started popping up in that country, apparently they’ve been an ongoing problem in the area of Asia under U.S. Pacific Command.

It’s easy to say that what happened last week was just some Chinese military personnel goofing around, maybe showing off with one of China’s new gadgets, and that this was utterly unsanctioned by Chinese military leadership. But this would be extremely naïve.

For one thing, it would be an awfully big coincidence if Chinese military personnel in several locations at different times over the past few months all had the same idea: “Let’s laser some U.S. planes.” It wouldn’t be at all surprising if this harassment was sanctioned by senior Chinese government and military officials. Chinese leaders aren’t fools, either. They know how to harass, but stop “just short of war,” as one Asia expert told The Wall Street Journal.

What’s more, these laser attacks are also wholly consistent with Chinese actions over the past several years while Beijing has been angling to rival the U.S. as a global superpower.

Let’s just take a few examples. First, China has been aggressively building up its military. For the past two decades, Beijing’s military budget increases have been in the double digits. In an assessment of China’s military power last year, the Pentagon noted that China is likely to build more military outposts like the one in Djibouti, perhaps in Pakistan. Last month, China held its largest ever naval drills, not surprisingly, in the South China Sea. This was followed quickly with live-fire exercises in the Straits of Taiwan.

Second, as most China-watchers are well aware, Beijing has been building up and militarizing man-made islands in the South China Sea in recent years. These actions present obvious problems to navigation in some of the world’s busiest international shipping lanes. Just last week, it was revealed that the Chinese had installed anti-ship cruise missiles as well as surface-to-air missiles on three of the disputed Spratly islands in the region.

Third, while most American media and political elites are hyper-focused on Russian interference and intelligence operations, few are keyed in on the massive intelligence and cyber espionage operations that China has been conducting against America in recent years, most notoriously the 2015 Office of Personnel Management hack that resulted in the theft of personal data belonging to nearly 80 million Americans.

Fourth, China has long backed the Kim Jong Un’s rogue regime in North Korea, and has proven less then helpful in curbing that country’s nuclear ambitions over the past few decades. Beijing likes to feign interest in doing so, but has ultimately not proven to be a reliable partner in that effort.

There are plenty of other indications of growing Chinese aspirations for regional hegemony and global leadership, including its Silk Road initiative, an increasingly aggressive posture vis-à-vis Taiwan, and its surging investment in Africa.

What this latest incident of Chinese laser tag shows is that China is testing its boundaries, not unlike a two-year-old. It is inching its way across various boundaries to see just what, exactly, it can get away with before America lays down the law, hoping to expand its power and position, not just in China’s sphere of influence in near-Asia, but also on the global stage. If it moves too fast, it might scare the international community. So it’s inching its way toward superpower status, testing the waters as it goes along.

And China will keep progressing apace if it’s not checked by the U.S. and its allies. The Trump administration has showed more willingness to push back than its predecessor, for example by increasing Freedom of Navigation Operations in the South China Sea. But the administration could do more. In reaction to the recent military installations in the Spratly Islands, the White House said, “We’ve raised concerns directly with the Chinese about this and there will be near-term and long-term consequences.” Great. But what, exactly, will that mean?

China takes a long view of history. Its willing to be patient and keep inching forward slowly, inuring the world to its growing dominance. If the U.S. doesn’t do something more to push back against Chinese aggression, we can expect to see more of the kind of harassment those U.S. airmen endured last week. And we can expect it to slowly ramp up.