A united front from the international community is the only thing likely to dissuade the growing threat of conflict by two of the most aggressive nations in the world. That means the United States needs to rapidly strengthen ties with our allies.

On Sunday, China sent 27 aircraft into Taiwan’s air defense buffer zone — 18 fighters and five bombers, along with a refueling aircraft. Taiwan responded by scrambling its own combat aircraft and activating missile systems to monitor the Chinese planes.

Such incidents are becoming more common, and each one raises the risk. Given China’s posturing and announced intent to retake Taiwan, which became self-governing in the wake of the Chinese Civil War. The intent seems to be twofold. First, China simply wants to show it can and will deploy warcraft in the immediate vicinity of Taiwan. Second, it wants that fact to intimidate the island. The fact each incursion acts as a rehearsal for an actual attack is also clear.

On the other side of the world, Russia is amassing troops near Ukraine. This isn’t the first time. Russia invaded Ukraine to take the Crimea in 2014. Its annexation of the territory is not recognized by most nations. And Russia backed Ukranian separatists including, it seems, with its own soldiers, in a simmering conflict in Ukraine’s east.

The United States estimates Russia currently has about 100,000 troops near the Ukrainian border. Russia’s intentions are less clear than China’s. Most analysts aren’t sure what Russia wants beyond a stronger hand in negotiations with Ukraine, especially given the international condemnation that would inevitably follow an invasion.

There are obvious, if imperfect, parallels in the two situations. China regards Taiwan as an actual breakaway territory. The island is where nationalist forces fled as they lost the mainland to the communist army. It’s a territorial claim that has some historical weight, if one frayed by more than 70 years of de facto independence.

Russia, by contrast, generally makes no territorial claim on Ukraine outside the Crimea. Ukraine has a long history as an independent nation and proved a substantial thorn in the Moscow’s side when it was one of the Soviet republics.

But Russia does claim Ukraine as part of its historical sphere of influence and views Ukrainian ties to the west (which are, ironically, strengthened by its own aggression) as a dangerous risk to its own security. Ukranian memories of Russian aggression and the Stalinist-era famine that killed millions remain strong and, with the effective secession of regions with large ethnic Russian populations, Russia’s ability to twist arms is as low as it has been in generations.

The U.S. would immediately be drawn into any invasion of Taiwan. Treaty obligations require the United States to come to Taiwan’s defense in the event of a Chinese invasion. Involvement in a war in Ukraine would not be obligatory, but it is likely the United State would offer aid short of direct involvement of American armed forces.

It would be far more preferable to avoid armed conflict in either case. And that course of action likely requires a show of unity beyond that which the international community has thus far shown. Chirps and squeaks of alarm don’t deter a predator on the hunt. An alerted and wary communal defense does.

International coalitions since World War II have largely depended on the leadership of the United States, and for good reason. Despite challenges, American leadership has been the most consistent guarantor of western goals. No other nation can project both the power and authority we can.

But projecting power is hollow if it is done outside the framework of cooperation. Should the United States attempt to do so alone, the means would be little different from those of our authoritarian opponents.

Efforts to reach an understanding with our allies about what the response to both Russia and China should be are urgently needed. Such a response cannot be ad libbed. It must be planned and coordinated, with each nation possessed of a clear understanding of goals and roles.

American resolve won’t deter either aggressor. But united resolve just might. Our allies need American support. But we must realize that we need them no less.