In the early hours of Oct 27, the USS Lassen, an American guided missile destroyer, sailed within 12 nautical miles of two Chinese-built artificial islands in the South China Sea - triggering weeks of heated diplomatic exchanges between the United States and China.
The move - called a freedom of navigation patrol by the US and an "irresponsible" and unprecedented act of provocation by the Chinese - caught many off-guard.
The US had dropped hints just hours earlier that the operation would take place and subsequently avoided saying anything at all about the voyage apart from confirming that it did take place.
Still, during a year when tensions between the US and China spiked in the region over Beijing's aggressive land reclamation works, the naval operation was perhaps the marquee clash.
For much of the year, the US had urged China to stop its aggressive island-building activity in contested waters. While other claimants had done land reclamation of their own, Beijing's projects were noteworthy for their scale and speed.
The USS Lassen's voyage effectively made concrete what had been purely verbal exchanges.
The two sides clashed over the matter again during the Asean Summit and the Asia-Pacific Economic Cooperation Summit a month later. In fact, Asia-Pacific defence ministers meeting ahead of the two summits scrapped plans for their customary joint declaration as they could not agree on language on the South China Sea.
All in all, it has been a tumultuous year in the South China Sea, and it remains unclear if 2016 will be any better.
Jeremy Au Yong