by JAMES SIMPSON

For eight days in September, a Chinese Song-class attack submarine made a highly unusual port call in Sri Lanka. For one, the diesel-powered vessel had the honor of being the first Chinese submarine to dock at an Indian Ocean port.

The news raised concerns across the region that China is muscling in on India’s traditional sphere of influence. Chinese state media coverage also provided a glimpse inside the submarine force—literally—and Beijing’s surprise at the controversy the visit created.

The submarine arrived at the Colombo International Container Terminal—a port facility built with millions of dollars in Chinese funding—one day before Chinese Premier Xi Jinping visited Sri Lanka.

The stop was just one part of the submarine’s journey. Chinese naval forces patrol around Somalia, and escort civilian ships through the pirate-riddled waters. And the Song-class submarine was on its way to join them, according to Col. Geng Yansheng, a Chinese military spokesman.

This year is the sixth since the People’s Liberation Army Navy first set sail for the Gulf of Aden. Its warships escort more than 1,000 commercial vessels every year. On several occasions, Chinese ships have responded to pirate attacks on civilian merchants.

The Song-class sub at Sri Lanka is all part of China’s latest escort flotilla. Beijing is emphatic that the stopover at Colombo should be no cause for concern.

“It is a common practice for navies of all countries to have their submarines and ships replenished at certain intervals at ports,” Geng said.