During the Spanish Civil War, Nationalist forces advancing on cities such as Madrid relied on what was called a fifth column, a covert network of sympathisers within Republican-held territory who worked to undermine the government from within. Could a similar scenario unfold in Taiwan? According to a former Taiwanese military intelligence director, more than 5,000 people are operating in Taiwan on behalf of the Chinese government.

The activation of a fifth column to incite civil unrest across Taiwan could be highly effective. It could debilitate Taipei’s ability to govern and maintain stability, potentially by exploiting existing fault lines in Taiwanese politics. This could provide Beijing with a pretext to deploy what it might call stabilisation forces. A fifth column could plausibly target critical infrastructure, disrupting power grids, railways, air traffic control and water treatment facilities. Bomb threats, arson attacks and incitement of riots would further destabilise society. Combined with Beijing’s formidable cyber capabilities, China could sow chaos and division while publicly denying any involvement. This would give Beijing the opportunity to shape the narrative, spread propaganda and justify intervention as a response to what it could claim is an internal matter.