As China continues to transform disputed territory in the South China Sea into features capable of sustaining air and naval bases, Vietnam is also upgrading areas it occupies.

Images taken by DigitalGlobe satellites in September show new facilities, including a possible dry dock, at West London Reef in the Spratly Island chain, around 680 km southeast of Ho Chi Minh City, that could allow boats to stop for maintenance and patrol for longer periods.

While the work is vastly outweighed by what China is doing, it suggests Hanoi wants to hold its ground over the contested waterway even if it risks upsetting Beijing.