Just upon its arrival at the Gulf of Aden towards dusk on Christmas Day in 2009, the frigate Chaohu received its first task - to escort the Chinese bulk carrier Dexinhai 800 nautical miles away.

At that time, the ship had been hijacked in late October - with 27 crew aboard, dangerously short on food, drinkable water and fuel - and was still under the control of pirates waiting for a negotiated ransom to be paid.

After 38 hours of high-speed sailing, the frigate arrived at the waters east off the Somali coast, where the pirates were watching closely around the bulk carrier.

Any mistake could have led to the failure of all previous rescue efforts.

The frigate kept patrolling about 20 nautical meters away from the Dexinhai, watching for any emergency.

At 8 pm, the instructions came. Soldiers, carried by a helicopter, landed on the deck of Dexinhai, immediately gained control of the ship and rescued the 27-member crew.

This was just one of the 666 vessels that frigate Chaohu has escorted in its 276-day mission in the pirate-infested waters off the Somali coast.

By October this year, Chinese convoys have rescued 26 ships and escorted 3,736 others since they joined the international mission in December 2008, official statistics show.

Designed and made in China, the frigate Chaohu created a record among the Chinese convoys for conducting missions for the longest periods of time while escorting the largest number of ships - both from China and other nations.

Proud of the achievements, officers and soldiers also have endured severe challenges for their physical and psychological health.

Working in the engine room means high exposure to noise, humidity, and heat for at least eight hours a day, which consumes much physical strength.

Flight Sergeant Xu Ce, for one, has to keep staring at the radar screen for long periods of time each day. The consequences have been serious: his eyes suffered from conjunctival congestion.

But Xu refused to take sick leave as suggested by a doctor, "I cannot leave with my job unfinished," he said.

At the intervals of tasks, officers and soldiers on the frigate have maintained a busy schedule of training. They have daily trainings such as shooting and simulating confrontations with pirates.

"We keep training, learning and improving coordination plans to stay at combat-status and at the call for any emergency," said Li Jixiang, leader of one of the teams on the frigate.

In addition to technique trainings, soldiers are also required to learn English, as they have to communicate with fleets of other countries from time to time.

"We learn daily expressions to improve conversational skills. This is what we must do to improve efficiency in conducting missions," said Jiang Ketian, a coach on the frigate.