The exercises in the Kyushu region will see the nations take part in air, land and sea drills, while Australia has sent a naval ship to support the operation involving around 300 troops, fighter jets, 10 surface vessels and a Japanese submarine.
This is expected to be the first of several joint military exercises conducted by Japan in the region. A British aircraft carrier and a German naval vessel are set to head to the Indo-Pacific waters later in 2021.
The military activity comes amid growing tensions between China and other countries in the region, as they accuse Beijing of engaging in aggressive military activity to solidify control of the East and South China Seas.
Conversely, China has argued that the basis for the "tense situation" is America's military encroachment in the area and its decision to "unreasonably" make accusations about Chinese activity. It claims that "instability and security risks" are coming "mainly from outside the region."