The US needs its own grey-zone tactics in the South China Sea

Passive resistance to Beijing’s actions in the South China Sea is not working. If the United States wants to win in the region, it needs a grey-zone strategy of its own.

Beijing has spent a decade refining a playbook that stays deliberately below the threshold of armed conflict. Chinese coast guard ships ram Philippine vessels, maritime militia swarm disputed reefs, and drones shadow foreign ships. Washington’s response – patrols, joint statements and expressions of concern – has imposed few costs and changed little.

This passivity means that China isn’t being deterred. Indeed, it’s being reassured that it can keep getting away with what it’s doing.

The US doesn’t need ships built for ramming to change that calculation. Rather, it should play to its strengths: a vast intelligence, surveillance and reconnaissance network, powerful cyber and electromagnetic warfare capabilities and a web of regional partners. The US military’s F3EAD targeting cycle (find, fix, finish, exploit, analyse and disseminate) offers a template for response. For grey-zone competition, it can be adapted into F2RED: find, fix, respond, exploit and disseminate, with calibrated non-kinetic responses replacing the kinetic component (the ‘finish’).

The first two steps of the cycle that could be applied to the South China Sea are largely in place. Intelligence, surveillance and reconnaissance assets across the region already track Chinese coast guard, navy, and maritime militia vessels, and coordination with partner forces can expand the network even further. But after that there’s a gap, because of Washington’s reticence to respond with any operation that may cause escalation.

One response below the threshold of armed conflict is to apply soft-kill effects – that is, nothing with kinetic impact, at least not on anything very costly or with people in it. When Chinese vessels launch uncrewed aircraft to harass or surveil ships of US partners, allied forces can jam or bring down the drones on the spot. Operations can be conducted against Chinese drones elsewhere to divert Beijing’s attention from the area of tension. The same tools become more potent against larger, more expensive ships and aircraft. Crucially, these effects must be paired with signalling, making it clear to Beijing that if its vessels don’t break contact with partners, costs will follow.

Cyber is a second channel for imposing costs. Beyond highlighting Chinese cyber actions against the US and its partners, the US can integrate offensive cyber capabilities into the ‘respond’ phase. By imposing proportionate costs on Chinese government, military or coast guard entities or networks, the US can signal that continued Chinese grey-zone actions will have consequences. For example, if a Chinese vessel rams a Philippine ship, the US could respond by disrupting critical systems associated with Chinese maritime operations. Because such capabilities can be employed from outside the immediate area of a dispute, they also provide strategic depth and another means of responding to Chinese coercion.

The US Coast Guard and Navy can work alongside partner coast guards to block, stop, and arrest militia or fishing crews caught operating illegally in partner waters. The principle is simple: partners enforce their own laws in their own waters, with US ships and intelligence backing them. This must stay strictly legal and be confined to those breaking international law and the law of US partners. Done properly, it turns Beijing’s favoured tactic, coercion dressed as law enforcement, back on itself, but from firmer legal ground.

Financial tools should be tied to response options. In 2022, the US Treasury sanctioned Chinese distant-water fishing companies, adding more than 150 vessels to the Specially Designated Nationals list over human rights abuses and illegal fishing. Extending that precedent to illegal fishing and militia activity within the region would mean freezing assets and persuading banks to cut their ties, further complicating militia and fishing operations and imposing additional costs.

The last two steps in the chain – exploiting and disseminating – are where the US holds its greatest advantage. It already operates extensively with regional partners, so the infrastructure for sharing information exists. It simply needs to be expanded to countries bullied by China.

That should include tracking data. If China can ram Philippine ships in Philippine waters, Manila should receive the information it needs to enforce its own rights, lawfully, in waters that Beijing claims. That should involve all of the aforementioned strategies supported by US capabilities – enforcing exclusive economic zones by arresting illegal fishing vessels, partnering with the US to jam Chinese drones within those areas, or using US intelligence, surveillance and reconnaissance networks to identify and remove Chinese intelligence and surveillance sensors within partners’ territories.

A US–China hotline could accompany all of this, alerting Beijing before the response phase commences and giving it a chance to back down.

Critics will warn that all this would risk escalation, and in the short term some friction would be likely. But Beijing currently pays nothing for testing its neighbours, and it will keep testing them until it pays much more. Demonstrating resolve, rather than tacitly accepting Chinese sovereignty claims, is more likely to lead to de-escalation over time.

Additionally, many regional states dislike China’s bullying but lack the resources to resist it alone. Seeing Washington finally impose costs, lawfully and alongside partners, could stiffen the resolve of those fence-sitters. In grey-zone competition, passivity is a strategy that’s working in Beijing’s favour.