The Chinese People's Liberation Army Navy now has an aircraft carrier, new jet fighters to fly off the flattop and even new submarines and guided-missile destroyers able to protect the refurbished Soviet carrier. And with the successful first sea trials of two new, 590-foot-long fleet oilers – tanker ships designed to keep other vessels fueled, or "replenished," while sailing long distance – the PLAN could soon be able to deploy all this new hardware beyond coastal waters.

"Replenishment vessel construction rate will be a particularly revealing barometer of the PLAN’s future expeditionary intentions," wrote Andrew Erickson, an analyst at the U.S. Naval War College. The more new oilers, the farther China will be able to send its new capital ships. Without underway replenishment, most naval vessels can travel only a few thousand miles; with fuel top-offs, they can circle the globe.

The latest, upgraded Qiandaohu-class oilers, also known as Type 903s, were launched at a shipyards in Guangzhou and Shanghai last spring. After additional work, the tankers began sea trials in the China Seas, testing out the vessels' mechanical systems plus the storage tanks, valves, hoses and other gear for refueling other ships at sea. This week the first of the new Qiandaohus reportedly completed her trials, clearing her for frontline use.

When it comes to prepping new naval vessels for service, nine months is not a long time. Many U.S. vessels take years to go from launch through trials to commissioning. One U.S.-based Chinese military analyst, who blogs under the pseudonym "Coatepeque," calls the oilers' speedy trials "impressive."

"The China navy must be needing those new milk cows bad," Coatepeque wrote.

He's not wrong. Prior to the introduction of the new Type 903s, the PLA Navy possessed just a handful of smaller oilers, including refurbished Soviet vessels and two of an earlier version of the Qiandaohu class: just five tankers in total to support a combat fleet numbering no fewer than 75 major warships, including frigates, destroyers, amphibious assault ships and the lone carrier. The U.S., by contrast, possesses more than 30 underway replenishment ships – all of them larger than China's oilers – to support around 130 large surface warships.

Outwardly similar to commercial tanker ships, the military oilers are deceptively simple vessels. Their basic equipment hasn't changed much in a century, but the techniques for using oilers are some of the most difficult to master in any navy.

To fuel up another ship, the oiler and the receiving vessel must match speeds and close within a few score yards of each other. Crews use special guns to launch lines between the vessels, then use the lines to haul across fuel hoses – all while the ships continue sailing. "It takes a crew adhering to strict safety practices to make an underway replenishment happen without incident," according to Military Sealift Command, which operates U.S. oilers.

The shortage of oilers (referred to as "AORs" in military shorthand) and likewise the PLAN's inexperience operating such ships, has imposed serious limitations on China's ability to deploy naval forces beyond the China Seas. Regular counter-piracy patrols in the Indian Ocean plus the occasional exercise near Japan has stretched the oiler fleet beyond its capacity. "With only five AOR in its orbat, it can barely keep up," Coatepeque wrote of the Chinese navy.

With the existing AOR fleet tapped out, the new carrier Liaoning would have forced Beijing to make a hard choice: keep the flattop in home waters or cut either the counter-piracy patrols or the long-range training cruises.

By the same token, the two new Type 903s will give the Chinese Communist Party options. Provided the carrier, her planes, escorts and other supporting forces function as advertised – and those are big ifs – China now has a large, potentially powerful warship that, with oiler support, can sail thousands of miles away to fly the flag, or fight a war.