In the 5th century BCE, Greece was unstoppable. When Persian King Darius led a massive army to invade in 490 BCE, the Greeks won a great victory at the Battle of Marathon (First Persian War). A decade later, when his son Xerxes invaded under the banner of revenge, they defeated him at the Battle of Salamis (Second Persian War). Athens played the leading role in both national crises. To prepare for another Persian invasion, Athens formed the Delian League in 478 BCE—a collective defense system that included some 150 poleis (city-states) along the Aegean coast.
Over time, however, Athens as the league's hegemon began to pressure its allies with its power. Member states, though varying by economic capacity, were forced to bear increasing burdens of warships and contributions. Athens even moved the common treasury from the island of Delos to Athens itself, controlling allied coffers at will—yet no member state protested. When building the Parthenon on the Acropolis, Athens drew upon treasury funds.
Cracks began to appear in the Delian League as mutual trust eroded. Allied states including Megara, Naxos, and Thasos announced their withdrawal, declaring they could no longer bear their contributions. Though such "alliance decoupling" proliferated, Athens responded with port bans and even military invasions. The contemporary historian Thucydides remarked it was "democracy in form only." The Delian League, its foundations shaken by allied unrest and defections, eventually ceded hegemony to the Peloponnesian League—a coalition of Sparta, Corinth, and Thebes. Defeated in the Peloponnesian War in 404 BCE, the Delian League dissolved, and Athens' golden age came to an end.
Mark Twain, revered as the father of American literature, famously said: "History doesn't repeat itself, but it often rhymes." US President Donald Trump, now engaged in conflict with Iran, is displaying an irrational view of alliances. When European nations showed lukewarm responses to American requests for support, he stated he was "strongly considering withdrawal from NATO." This threatens to discard the "Atlantic Alliance" between the US and Europe—which has maintained the balance of power against Russian expansion—like worn-out shoes.
Trump has also taken aim at Korea. The president has repeatedly cited Korea's failure to dispatch warships to open the Strait of Hormuz, reacting irritably: "Korea didn't help us either. They actually tried not to help." Just as the US relocated USFK air defense assets to the Middle East, it may alter the character of the Korea-US alliance and USFK policies according to American strategic calculations and interests. The "values-based alliance" that stood firm for 72 years since the signing of the Mutual Defense Treaty in 1953 could degenerate into a "balance sheet alliance" that fluctuates based on defense and security profit-and-loss calculations.
The same applies to economics and trade. Even as the Strait of Hormuz blockade persists due to US attacks on Iran, Trump has shown an evasive attitude, saying Korea, Japan, and the EU should "handle it themselves." Moreover, citing Korea's excessive trade surplus with the US, Washington has pressured Korea for $350 billion (approximately 500 trillion won) in US investment, and has added agricultural products, high-precision maps, AI infrastructure, online platform laws, and pharmaceuticals to its list of trade barriers. We cannot rule out the possibility that the US will wield Section 301 of the Trade Act like a sword, combining additional tariffs with non-tariff measures. Fair trade based on free trade agreements has vanished, replaced by a fervent pursuit of "alliance impoverishment" policies that squeeze partner economies for one's own benefit.
While the rock-solid Korea-US alliance is unlikely to follow the exact path of the Delian League, we must remain vigilant that cracks could form in the alliance and prepare countermeasures in advance. The US could strongly pressure Korea to repurpose USFK for China's expansion in the East and South China Seas. As Korea expands its trade surplus with the US through superior technology and price competitiveness, Washington may brandish an even sharper trade law blade. If we remain complacent, we could fall into a "multiple dilemma"—a critical situation indeed. This is not limited to the Trump administration. Regardless of which US president takes office in the future, the "balance sheet alliance" is likely to become a constant rather than a variable. The halcyon days of the Korea-US alliance are ending. In both economics and defense, self-reliance is the only key to survival. Are we truly preparing proper strategies for what lies ahead?