The recent state visit of Philippine President Ferdinand Marcos Jr. to Hanoi was the latest sign of the growing strategic convergence between the Philippines and Vietnam regarding maritime security and the South China Sea. Building on a range of past efforts, both leaders confirmed an agreement on coast guard cooperation and a future bilateral code of conduct for the South China Sea. Marcos also invited Vietnam to participate in the multilateral naval exercise MARPOLEX in the Philippines later this year, alongside Indonesia and Japan.
This convergence of views between the two countries comes at a time of heightened tensions in the South China Sea, generated by a growing Chinese assertiveness and its use of an ever-growing set of area denial capacities, hybrid warfare techniques, and grey zone tactics. This has resulted in a string of dangerous incidents around several Philippine-claimed features, such as Scarborough Shoal, Second Thomas Shoal, Whitsun Reef, Iroquois Reef and Sabina Shoal, and in and around Vietnam’s exclusive economic zone, either near Triton Island or in the Vanguard Bank area.
Despite this shared threat, the Philippines and Vietnam haven’t always seen eye to eye on the disputes in the South China Sea, where their own outstanding maritime and territorial disputes have inhibited maritime cooperation for many years. This was a subject of tension after normalization in 1976, which took place shortly after Saigon’s surprise takeover of Southwest Cay in the Spratly Islands the previous year. This helped prompt then President Ferdinand E. Marcos, the father of the current Philippine leader, to publish a Presidential Decree in 1978, formally establishing the Philippines’ claims in the Spratly Islands.
The decree marked the start of a race between Manila and Hanoi to establish control over a maximum number of maritime features in the Spratlys. That same year, the Philippines took possession of Lankiam Cay, Commodore Reef, Loaita Cay, Loaita Island, and Northeast Cay, while Vietnam took control of Amboyna Cay, Central London Reef, Grierson Reef, and Pearson Reef.
Despite these frictions, the Philippines and Vietnam have seen a gradual convergence of interests as both have come to face a more serious maritime challenge from China, which has asserted expansive claims to nearly the entire South China Sea.
Both nations have lost national territories to China in the South China Sea. Vietnam suffered humiliating losses in the Paracel Islands in 1974 and at Johnson South Reef in the Spratly Islands in 1988, which China has occupied ever since. Manila’s losses were bloodless but no less humiliating. In 1994, China seized Mischief Reef, which it subsequently transformed it into a major military base squarely in the middle of the Philippines’ exclusive economic zone, which it is now using to support its ongoing blockade of the beleaguered outpost on Second Thomas Shoal. China’s 2012 seizure of the Philippines’ important fishing grounds at Scarborough Shoal was also a serious setback for Manila.
Over the past decade, as China has become more and more active in asserting its maximalist claims, Vietnam and the Philippines have seen significant developments in maritime cooperation. The Philippine-Vietnam Action Plan (2011-2016), signed in 2011, included a memorandum of agreement to establish a hotline between the Philippine Coast Guard and Vietnam’s Marine Police, as well as a memorandum of understanding to enhance mutual cooperation and information sharing between the two countries’ navies.
In 2014, the two countries also engaged a series of trust-building measures, including playing football and volleyball matches at Vietnamese and Philippine-held features in the Spratlys. In 2016, Hanoi also issued statements in support of the Philippines’ South China Sea arbitration case against China; and in 2019, the two sides signed a bilateral fishing agreement. A good example of the success of that last agreement is that Vietnam’s coast guard recently saved 20 Filipino fishermen stranded at sea after their ship was rammed by a Chinese vessel, which also bolstered Vietnam’s public image in the Philippines.
The Philippines and Vietnam also signed a strategic partnership in 2015; established dedicated hotlines to allow for permanent and seamless communication between their respective fisheries (2015) and coast guards (2024); initiated staff-to-staff meetings; arranged the port call of two Vietnamese destroyers (Dinh Tien Hoang and Ly Thai De) in Manila in 2014; and recently relaunched a marine scientific research agreement (2021).
In November 2023, Marcos raised the possibility of establishing a code of conduct with Malaysia and Vietnam, which would help appease the situation in the South China Sea after decades of tensions and disputes. The repeated announcement by the Philippines of some pact between Malaysia, Philippines and Vietnam has generated a lot of attention, but details are vague, and the arrangement seems to have been downgraded to a bilateral code of conduct during Marcos’ visit to Hanoi. Still, such an agreement, should it come to pass, would make sense in light of the maritime security challenges that Hanoi and Manila face from an increasingly aggressive Beijing. According to the Center for Strategic and International Studies’ China Power Project, Vietnam and the Philippines have suffered the brunt of China’s belligerence in the South China Sea, experiencing 50 percent and 25 percent respectively of all major confrontations between 2010 and 2020.
The two countries also have good reasons to doubt the prospects for an ASEAN-China Code of Conduct, which has made little or no progress since talks on the agreement began in 2002. The negotiations on the current ASEAN-China Code of Conduct remain stalemated over China’s refusal to include either the Philippine-claimed Scarborough Shoal or the Vietnam-claimed Paracel Islands in any agreement, as it already controls both. Moreover, the question of what authority would enforce such a code seems hopelessly clouded.
Marcos has expressed his nation’s frustration at the slow progress on the Code, while now-regular incidents of Chinese aggression at Scarborough Shoal and Second Thomas Shoal, on top of the regular and illegal presence – and environmental damage – of the Chinese maritime militia at Philippine-occupied Iroquois Reef, Whitsun Reef, and Sabina Shoal, have prompted his pursuit of bilateral and minilateral talks. It is for this reason that Marcos has called Vietnam “Manila’s sole strategic partner in Southeast Asia” and maritime cooperation “the cornerstone of the bilateral relationship.”
To be sure, while both the Philippines and Vietnam have taken steps to beef up their deterrent capacity and reinforce their presence on disputed shoals and islets, there are a number of obstacles to further convergence between the two countries. These include their differing political systems, the good relations between the Vietnamese and Chinese communist parties, and the disjuncture between Hanoi’s policy of “strategic hedging” and Manila’s formal security alliance with the United States.
The two nations have also yet to resolve their overlapping claims in the Spratlys, the cause of the aforementioned tensions in the late 1970s, and also both have unresolved claims with Malaysia. Given that another territorial dispute between the Philippines and Indonesia, on the continental shelf delimitation in the Celebes Sea, took nearly 25 years to resolve, it is unlikely that such disputes will be settled any time soon even if growing tensions with China have led to progress in the negotiations between other countries, such as the Vietnam-Malaysia joint submission on the continental shelf of 2009 and the 2022 maritime boundary agreement between Vietnam and Indonesia.
That maritime cooperation between the Philippines and Vietnam has advanced to such a degree despite these outstanding disputes points to the seriousness of the challenges that the two nations now face from China. While there are probably limits to how far this convergence can proceed, Philippine-Vietnam bilateral relations are well underway to becoming a long-lasting and mutually beneficial partnership – a process which Beijing, for its part, can be expected to make as difficult as possible.