ARDB is Japan's first amphibious warfare brigade since World War II, comprised of around 2,100 troops.
A recent 20-minute exercise showed how Japanese forces would recapture an island from invaders.
Japan has been at odds with China over the control of remote, uninhabited islands on the East China Sea. The dispute has strained ties between the two countries due to the potential economic value — such as oil and gas reserves, shipping lanes, and fishing grounds — in the area.
"Given the increasingly difficult defense and security situation surrounding Japan, defense of our islands has become a critical mandate," Japan vice defense minister Tomohiro Yamamoto said in a speech.
next slide will load in 15 secondsSkip AdSkip AdThe ARDB was reportedly modeled after the US Marine Corps' Marine Expeditionary Units and received advice from US liaisons.
The ARDB is expected to be upgraded to around 3,000 troops, 17 V-22 Ospreys, and 52 Amphibious Assault Vehicles.
Although countries like China greatly outspend Japan in defense spending, some analysts believe Japan's armed forces could "stand toe to toe with anybody."
"The Amphibious Rapid Deployment Brigade will show to the international society our firm resolve to defend our islands," a senior Defense Ministry official reportedly said.