We have heard much about the policy differences separating the Trump and Obama administrations, but little about areas of common ground. One such area appears to be their convergent approaches to China’s attempt to annex the South China Sea by constructing artificial islands atop reefs in international waters.

To date, Beijing has built up some 3,000 acres of instant islands in the resource-rich region. In response, the Obama administration began conducting freedom of navigation operations (FONOPs) around these made-in-China islands in 2015. There is every indication the Trump administration intends to expand on these operations and thus defend a rules-based order in the Asia-Pacific.

Before getting into some of the specifics of South China Sea FONOPs, it’s important to detail why the United States and its allies are engaging in this mission.

Simply put, what China is doing undermines the peace and prosperity of the Pacific.

China is laying claim to 90 percent of the South China Sea based on a map created by Chinese cartographers in 1947, flouting international norms and turning reefs hundreds of miles from its territorial waters into military outposts.

Beijing’s goal: to control the resource-rich South China Sea and muscle the United States out of the Western Pacific. As Prime Minister Shinzo Abe of Japan puts it, China is trying to turn the South China Sea into “Lake Beijing.” No doubt reflecting the views of his government, Chinese Vice Adm. Yuan Yubai says, “The South China Sea, as the name indicates, is a sea area that belongs to China.” (By that logic, the Gulf of Mexico belongs to Mexico and Indian Ocean to India.)

Bolstered by its instant islands, China is asserting these claims in fait accompli fashion. Satellite images detail Beijing’s brazen island-construction operations. These instant islands have obvious military applications. According to the U.S.-China Economic and Security Review Commission, “China appears to be expanding and upgrading military and civilian infrastructure – including radars, satellite communication equipment, antiaircraft and naval guns, helipads and docks – on some of the man-made islands.” One of the islands has a 10,000-foot airstrip – big enough for long-range bombers and fighter-interceptors.

True, Beijing is not trying to lop off part of Venezuela (like Kaiser Wilhelm II in 1902), or annexing the Sudeten in the heart of Europe (like Adolf Hitler in 1938), or declaring Kuwait “Province 19” (like Saddam Hussein in 1990). But the principle is the same. As they bully weaker neighbors and dot international seaspace with man-made islands, China’s leaders are taking what’s not theirs. The lesson of Munich teaches that it’s better to confront such aggression than to appease it.

American policy After months of warning Beijing that the U.S. Navy would challenge China’s illegal bid to seize a large swath of the South China Sea, the Obama administration ordered the destroyer USS Lassen in late 2015 to defend freedom of the seas and to sail within 12 miles of an artificial island built by China on Subi reef. Beijing called the operation “dangerous and provocative.”

Beijing’s assertions notwithstanding, there’s nothing new or provocative about the Navy challenging this sort of lawlessness. America has been keeping the open seas, well, open for 215 years.

In the 18th and 19th centuries, the Barbary States required ships traveling near their waters to pay tribute to guarantee safe passage. The United States complied – until Thomas Jefferson became president. He initially proposed an anti-piracy coalition with Europe “to compel the piratical states to perpetual peace.” When that didn’t work, Jefferson concluded, “It will be more easy to raise ships and men to fight these pirates into reason, than money to bribe them.”

As the Congressional Research Service reports, between 1801 and 1870, U.S. forces waged a far-flung war against piracy – and for freedom of the seas – in Tripoli, Algiers, Greece, Ivory Coast, Hong Kong, Sumatra, the Caribbean and the Gulf of Mexico.

In the 20th century, President Woodrow Wilson’s 14 Points called for “absolute freedom of navigation upon the seas.” President Franklin Roosevelt called “freedom of the seas” an “American policy.”

Since 1979, U.S. forces have challenged excessive airspace and coastal claims around the world under the Freedom of Navigation program. Thus, when Libya’s Muammar Qaddafi declared the Gulf of Sidra as his own, the Carter administration ordered U.S. warplanes and warships into the area from time to time, although it suspended the exercises during the Iranian hostage crisis.

When the exercises recommenced at the beginning of the Reagan administration, Qaddafi sent his air force into international airspace to challenge the Americans. The Navy responded with deadly force and made it clear to Qaddafi that there would be no payoff for disregarding international norms – only costs.

Likewise, when Iran began attacking commercial ships in the Persian Gulf during the Iran-Iraq War, President Ronald Reagan ordered Kuwaiti ships reflagged with the Stars and Stripes and had U.S. warships escort Kuwaiti vessels. After an Iranian mine ripped through a U.S. ship in international waters, Reagan launched a series of military strikes against Iran. “By the end of the operation, U.S. air and surface units had sunk, or severely damaged, half of Iran’s operational fleet,” a Navy report recalls.

Burdens Today, 90 percent of global trade travels by sea, and $5.3 trillion of global trade passes through the South China Sea annually (including $1.2 trillion in goods headed to or from the United States). This doesn’t happen by accident or by magic. The burden of keeping the sea lanes open – discouraging encroachment and illegal claims, deterring bad actors, fighting piracy, clearing vital waterways and chokepoints – largely falls on the Navy. In 2015, the most recent year with available data, the U.S. military made “operational assertions” against excessive maritime claims of 13 nations. China was at the top of the list.

The Trump administration seems ready to grab the baton:

• President Donald Trump worries that China is building “a military fortress” in the South China Sea and vows to build the Navy back to 350 ships. Such a buildup is needed: “For us to meet what combatant commanders request,” according to former Chief of Naval Operations Adm. Jonathan Greenert, “we need a Navy of 450 ships.”

• Defense Secretary James Mattis has expressed support for continued FONOPs in the South China Sea, declaring, “The bottom line is that international waters are international waters and we have got to figure out how do we deal with holding on to the kind of rules that we have made over many years that led to the prosperity for many nations, not just for ours.”

• Secretary of State Rex Tillerson adds, “We’re going to have to send China a clear signal that, first, the island-building stops. And second, your access to those islands also is not going to be allowed.”

• The Pentagon plans to begin sailing within 12 nautical miles of artificial islands Beijing has illegally built near the Spratly and Paracel island chains, Navy Times reports, adding, “The plans are heading up the chain of command for approval by President Donald Trump.”

Already, America’s allies are sending clear signals about their commitment to freedom of the seas.

Japan plans to expand its naval activity in the South China Sea by conducting joint patrols with the Navy as well as exercises in international waters claimed by China. “I strongly support the U.S. Navy’s freedom-of-navigation operations, which go a long way to upholding the rules-based international maritime order,” Japanese Defense Minister Tomomi Inada says. “Japan, for its part, will increase its engagement in the South China Sea.”

Australia conducts air patrols over the South China Sea to ensure freedom of the seas and skies. The Australian military reports that it has increased the number of patrols and that China challenges “nearly all” of its flights in the area. Royal Australian Air Force Air Marshal Leo Davies says his nation is committed to “building and encouraging a rules-based global order” and “will work closely with our allies, partners and other like-minded air forces to determine how we can make a practical contribution to ensuring freedom of navigation.”

Calling the passage ways of the South China Sea “the main arteries” of international trade, Prime Minister Narendra Modi says India “supports freedom of navigation based on international law.”

Rhetorical and material support for FONOPs in the South China Sea is also coming from outside the region. French Defense Minister Jean-Yves Le Drian told attendees at a 2016 security conference that France would encourage the European Union to carry out “regular and visible” FONOPs in the South China Sea. “If we want to contain the risk of conflict, we must defend this right, and defend it ourselves,” Le Drian said. “Several times per year, French navy ships cross the waters of this region, and they’ll continue to do it,” Le Drian explained, noting that France is committed to “sailing its ships and flying its planes wherever international law will allow, and wherever operational needs request that we do so.”

Britain’s ambassador to the United States, Kim Darroch, vows that his nation will “play our part” in the Pacific. Toward that end, Britain announced in December plans to fly fighter aircraft through disputed parts of the South China Sea, and Britain plans to routinely steam its new aircraft carriers to the Pacific. “We absolutely share the objective of this U.S. administration, and the next one, to protect freedom of navigation and to keep sea routes and air routes open,” Darroch said late last year.

Enforcing the law If they want to prevent Beijing from becoming the self-appointed gatekeeper of the sea lanes in between the Philippines and mainland Asia, the United States and its allies must carry out frequent and unannounced FONOPs.

Before the Lassen conducted FONOPs in October 2015, the Navy had avoided sailing or flying near the disputed territories claimed by China for some three years. Equally troubling, there was a five-month gap between FONOP maneuvers in the South China Sea last year.

FONOPs also should be unannounced. In the weeks leading up to the Lassen’s maneuvers, Washington publicized plans to steam U.S. ships into and through the waters surrounding China’s instant islands. Just as I need not notify my neighbors of where, when or why I will be traveling the city streets, Washington, Tokyo, Canberra and other capitals are under no obligation to forewarn Beijing about plans to deploy assets in international seaspace and international airspace. In fact, doing so implies that China is owed such a forewarning, which implies that China has a special prerogative over the areas it claims. It does not.

It pays to recall that the United States and its allies are doing nothing more than observing (and enforcing) the law. A U.N. tribunal recently ruled against Beijing’s outlandish South China Sea claims. If China’s leaders fail to respect that ruling, the U.S. Navy and Air Force will be obliged to remind them – repeatedly – that their islands have no international legitimacy.

Of course, to carry out such an open-ended operation, America’s military needs more resources. To deliver those resources, Washington must end the bipartisan gamble known as sequestration. The defense budget has fallen from 4.6 percent of GDP in 2009 to 3.1 percent. As China builds up and builds out, this is the best way to invite the worst of possibilities: what Churchill called “temptations to a trial of strength.”