For several weeks starting in late December, Indonesian media was dominated by reports of a flotilla of Chinese fishing and coast guard vessels operating without permission in the country’s exclusive economic zone (EEZ). The situation strained bilateral relations, presented President Joko “Jokowi” Widodo with the first foreign policy crisis of his second term, and forced Indonesia to confront the uncomfortable fact that it is a party to the South China Sea disputes even if it does not claim any contested islands or reefs. But the public reporting from Indonesian officials was also contradictory and incomplete, leaving the scale and timeline of the standoff unclear.

It is impossible to track individual Chinese fishing vessels accurately because they either did not broadcast Automatic Identification System (AIS) signals or, with one brief exception, their transmissions were too weak to be detected. But AMTI, along with observers like the U.S. Naval War College’s Ryan Martinson, carefully tracked the AIS signals of Chinese law enforcement vessels escorting the fishing fleet. Four China Coast Guard (CCG) vessels and one provincial-level China Marine Surveillance (CMS) ship from Hainan accompanied the fleet during its operations near Indonesia. Their AIS transmissions provide a much clearer timeline of the operation. They show that it lasted longer than Indonesian authorities reported and began in the EEZs of Brunei and Malaysia.

On November 28, CCG 5403 sailed out of port in Hainan Province’s Sanya, headed south through the Spratly Islands, and turned east. On December 4 it entered the EEZs of Malaysia and then Brunei. The 5403 is a Zhaolai-class patrol ship and at nearly 5,000 tons it is considerably larger than both the coast guard and navy ships that Southeast Asian states might deploy to confront it. It joined the CCG 5202, which had arrived a day earlier. That ship had left the artificial harbor at China-occupied Subi Reef on November 29, made a detour into the northern reaches of Indonesia’s EEZ on December 1-2, and headed for Malaysian waters. At 2,700 tons, the Zhaojun-class 5202 is considerably smaller than the 5403, but it is also much better armed, sporting a 76-mm cannon.

For nearly a week, the two ships patrolled first Brunei’s EEZ and then Malaysia’s. The 1,300-ton CMS 2169 was with them during at least some, and perhaps all, of this. Its AIS was detected on December 8 alongside the 5202 and 5403—the first time it had been picked up since leaving Sanya on November 18. It would continue to only broadcast sporadically for the rest of the operation. If Brunei or Malaysia deployed government vessels to confront this Chinese incursion, they did not broadcast AIS. And unlike Indonesia’s later response, neither went public with evidence of Chinese fishing vessels in their EEZ. But that this coordinated group of law enforcement vessels was already escorting the same fishing boats they would soon lead into Indonesian waters seems very likely. Their patrols in Brunei’s EEZ in particular seem to have no other explanation.

On December 9, the 4,000-ton Shucha II-class CCG 5302 sailed from Mischief Reef to join the group in Malaysia’s EEZ. The next day, the 5202 broke away and sailed to Fiery Cross Reef in the Spratlys, presumably to resupply. The others headed southwest, entering waters claimed by Indonesia on December 11. This was more than a week before Indonesian authorities first reported the Chinese fishing presence in its EEZ. From December 11 to 19, the 5202, 5403, and 2169 operated freely in waters claimed by both Indonesia and Malaysia. On December 16, the first and only AIS signal from one of the fishing vessels they were escorting was detected. The Gubeiyu 88603 was seen briefly about 115 nautical miles from Indonesia’s Natuna Besar island.

Indonesian government vessels responded for the first time on December 19. The KN Tanjung Datu, a patrol vessel from the Indonesian Maritime Security Agency, or BAKAMLA, steamed out of Natuna Besar and patrolled near the fishing fleet before returning to port. It headed out again on December 21 and briefly approached the Chinese fleet before heading home. At 2,700 tons and carrying only small arms, the Tanjung Datu could offer no threat to the CCG ships.

Still its patrol seemed to have an effect, as the fleet moved farther east to an area straddling the Indonesian EEZ. Meanwhile the 5202 rejoined the group. After almost a week at Fiery Cross Reef, it had spent the previous five days patrolling around nearby Vietnamese-held features before rejoining its compatriots. The 2169 briefly broadcast AIS on December 21 and then went dark again. BAKAMLA would later report that it monitored 63 Chinese fishing vessels and two CCG ships in its waters between December 19 and 24.

Whatever effect the initial Indonesian patrols had was short-lived. On December 22, the Chinese fleet began to move steadily westward, deeper into Indonesia’s EEZ. The Tanjung Datu made its third patrol on December 24, this time in the direction of the 5202 as it had begun to make its way west. The 5202 appears to have received the message, turning around and heading back out of Indonesia’s EEZ.

But the effect was, again, temporary. The 5202 reentered Indonesia’s EEZ the very next day. By December 29, the 5202, 5302, and 5403 had all returned to the initial location that the Chinese fleet had occupied before December 19.

In response, the Indonesian Foreign Ministry summoned the Chinese ambassador and sent an official protest to Beijing on December 30. During his daily press briefing the next day, the spokesperson for China’s Ministry of Foreign Affairs offered a strident reply. He insisted that Chinese fishers have historic rights throughout the South China Sea and the CCG ships were “carrying out routine patrol to maintain maritime order and protect our people’s legitimate rights and interests in the relevant waters.” Both sides continued to issue heated public statements over the next several days.

At this point, the 5403 had been at sea for more than a month. On December 29 it broke off from the group and headed to Fiery Cross Reef to resupply. It left Fiery Cross on January 2 heading south and presumably rejoined the group, though there is a gap in its AIS data. The next day, the 5202 made its own resupply run to Fiery Cross, returning on January 6. To fill the gap, a fifth and final ship, CCG 46303, sailed out of Fiery Cross on January 5 and joined the cluster in the Indonesian EEZ. At more than 4,000 tons and sporting a 76-mm cannon, the Zhaoduan-class 46303 was the most capable and intimidating of the vessels engaged in the operation. It is unclear whether the 5302 and 2169 remained on-station in the Indonesian EEZ or also detoured to Fiery Cross during this period. There is a gap in the 5302’s AIS signal from January 5 to 8 while the 2169, as was its habit, broadcast only once on January 5.

This activity matches a pattern seen in other recent CCG actions. The availability of China’s artificial island bases in the Spratlys for resupply and replenishment has enabled sustained weeks- or even months-long deployments to the farthest reaches of the nine-dash line—something that was much more difficult for Chinese vessels in the past.

As the standoff continued, Bakamla deployed two more patrol ships to support the Tanjung Datu. Indonesia’s military sent 600 army and marine troops to Natuna Besar on January 3. The air force began regular surveillance flights with a Boeing 737 maritime patrol aircraft on January 5. By January 7, the navy had deployed six warships to the area and four F-16C fighter jets had landed on Natuna Besar ahead of a planned visit by President Joko “Jokowi” Widodo.

Meanwhile, the Chinese deployment entered its final phase as the fleet sailed north—farther from the Indonesian coast but still well within its EEZ. At his January 7 daily press conference, the spokesperson for China’s Ministry of Foreign Affairs was much more conciliatory, stressing the importance of friendship and cooperation to manage disputes. Jokowi landed in Natuna Besar on January 8, meeting with local officials, fisherfolk, and visiting the local naval base.

A day later, an Indonesian military spokesperson claimed that all Chinese vessels had left “as soon as the president arrived on the Natuna.” A senior BAKAMLA official confusingly said only the 5202 (which was identified by its previous name of CCG 35111) remained in “Indonesian continental waters.” Both announcements were premature. The 5202, 5302, 5403, and 46303 all remained in the Indonesian EEZ, presumably still serving as escorts for the fishing fleet, until January 11.

The Indonesian government must have realized its error by January 10 when it sent the Tanjung Datu out for one last look at the Chinese fleet. It approached to within a few miles of the vessels before returning home.

The Chinese fleet began its withdrawal on January 11, with the 5202, 5403, 5302, and 2169 all returning to Hainan by January 16. The 46303, having only joined the operation a week earlier, stayed at sea and took over patrol duty at Luconia Shoals off the Malaysian coast.

Since the Chinese flotilla dispersed, diplomats from Jakarta and Beijing have publicly focused on easing tensions. But the operation will have lasting effects. It has heightened awareness within Indonesia of the South China Sea disputes and the stakes involved for the country. And it highlighted several trends that are part of the new unstable status quo in this contested waterway. The operation showed yet again how much China’s Spratly Island bases facilitate larger and more sustained deployments of coastguard and paramilitary force. And while the CCG has escorted fishing flotillas around the Spratly Islands on many occasions, doing so in the EEZs of neighboring states far from contested islands is a new level of provocation. That Indonesia was targeted shows that even claimants who downplay the disputes and prioritize positive relations are subject to Chinese coercion and intimidation. This is especially true of Malaysia, which has experienced increasing levels of harassment despite its unofficial policy of not criticizing Chinese activities in its EEZ.