YINCHUAN, July 12 (Xinhua) -- China on Monday afternoon started a military drill at an unidentified training base in the northwest, with army units from different theaters.

The nine-day drill is the first cross-theater drill since China established a new command system in January.

Artillery from the 31st Army Group of the Eastern Theater Command joined the drill after marching 2,500 km, while its antagonist in the drill is a brigade from the 47th Army Group of the Western Theater Command.

The drill aims to train firepower applications in encounters, attack and defense, landing and anti-landing, etc. the army said.

From the middle of July to the end of August, the People's Liberation Army (PLA) Army will organize artillery brigades from all of the five theater commands to join cross-theater drills.