In commentaries tackling the treaty alliances of the United States, Thailand has often been referenced as its oldest Asian ally. Yet, some would also address the Philippines as the US oldest ally in Asia, so one—like myself—would be left confused. So, which of which is truly the oldest ally? Of course, it can’t be both unless they’ve forged an alliance simultaneously, right?

So, which of the two Southeast Asian countries is the oldest ally?

We’ll not be delving deep into the relationship history between US-Thailand and US-Philippines—especially with this one, which had a rather complicated history—But rather a brief discussion on what led these two Asian countries to vie for the “oldest” title.

Deep and Enduring

The diplomatic relationship between the US and Thailand was initially cemented around the mid-19th century, predominantly engaging in trading and commerce, and even reached a level of comfort that by the early twentieth century, Americans served the King of Thailand as foreign affairs advisers. They formalized this relationship with a Treaty of Amity and Commerce signed in 1833, the first-ever known American treaty to any Asian country. In 1954, both reaffirmed their alliance with the Manila Pact of the Southeast Asia Treaty Organization (SEATO). Though the treaty was dissolved in 1977, the Manila Pact continued to be enforced, along with other bilateral understandings like the Thanat-Rusk communique of 1962.

“The United States looks forward to strengthening the excellent cooperation between our two countries, as allies and friends. Next year marks 190 years of diplomatic relations.”

Then, in 2003, the US designated Thailand a major non-NATO ally with the 2012 and 2020 Joint Vision Statement, serving as the former’s security commitment to the latter.

Moreover, according to the WSJ, the US-Thailand forces frequently engage annually, including military exercises. They have collaborated closely, as well, in law enforcement. The Royal Thai Police and the US Drug Enforcement Agency have worked hand-in-hand against narcotics trafficking since 1963. Not to mention the strategic location of Thailand, positioned in the middle of the ASEAN—the heart of the Indo-Pacific Strategy of the US. Hence, for the latter to maintain its relationship with its long-standing ally not just make sense but is imperative.

Bittersweet Relations

The US and the Philippines have a long, complicated history after the former inherited the latter from the Spanish regime. But, bitter history aside, both countries have long-standing relations involving a broad range of areas of strategic security as well as political, developmental assistance, and economic cooperation. This relation has been brought together because of the Mutual Defense Treaty signed in 1951, making “the Philippines the oldest security ally of the US in Southeast Asia and among the five treaty allies of the US in the Pacific region, similar to the agreements signed by South Korea, Japan, and Europe’s NATO.”

“US-Philippine relations are based on strong historical and cultural linkages and shared democratic values and interests. Strong people-to-people ties, economic cooperation, and security and defense cooperation between the Philippines and the United States provide avenues to engage on a range of bilateral, regional, and global issues.”

At one point, the US had two military bases in the Philippines, one in central Luzon (formerly Clark Field) and one in Subic Bay (formerly Olongapo Naval Station), but because of deteriorating bilateral relationships and a devastating volcanic eruption in 1990, the US withdraw its military forces out of the latter country. Despite this, the military ties between the two countries weren’t severed, instead renewed in 1998 through a Visiting Forces Agreement (VFA), followed by the 2002 dispatch of the US Special Operations Forces to assist in fighting against the Islamic insurgents in the country, and, like Thailand, the designation of the Philippines as a major non-NATO ally.

The Philippines’ location has the potential to play a significant role in the US Indo-Pacific Strategy, which led to the 2014 Agreement on Enhanced Defense Cooperation that would provide the necessary equipment and financial aid. Invitations to participate in military exercises were also sent to the Philippine armed forces and casual usage of the Filipino airspace to surveil suspicious activities, especially with China over the South China Sea.

Furthermore, both countries have also forged a strong trade and investment relationship over the years, naming the Philippines as one of the largest foreign investors of the US.

Technically speaking, in terms of forming a security alliance, the Philippines is the US oldest ally, having penned an agreement in the 50s, while Thailand had only done this three years later with the Manila Pact. However, regarding trading connections and friendly engagements, Thailand holds the title of the oldest ally, with the 1833 Treaty of Amity and Commerce as proof of this trade and economic exchange.

Simply put, it depends on the commentary’s context and the definition of the term ally.