Editor's note: Tensions have escalated among China, Japan and the U.S. ever since China announced its installment of an Air Defense Identification Zone (ADIZ) in the East China Sea on Nov. 23.

Japan has called the set-up a "peace-disturbing act," and U.S. Secretary of State John Kerry and Secretary of Defense Chuck Hagel have both said the U.S. is "deeply concerned." From Nov. 26 to Nov. 28, U.S., South Korean and Japanese warplanes flew through China's ADIZ consecutively without informing China.

As an early-warning air defense concept, an Air Defense Identification Zone (ADIZ) is established by some countries off their coasts. Upon entering the zone, all aircrafts are required to identify themselves, report flight plans and inform ground control of their exact position.

The first ADIZ was established by the U.S. in 1950, when it created a joint North American ADIZ with Canada, citing the legal right of any nation to establish reasonable conditions of entry into its territory. More than 20 countries, including the U.S., Canada, France, Germany, the United Kingdom, Australia, South Korea and Japan, have demarcated Air Defense Identification Zones in high seas or international waters. Japan, South Korea and China's Taiwan region have their ADIZs respectively in the East China Sea.

Why has China's creation of an ADIZ caused so much havoc? Why would not the U.S. and Japan like to respect China's legitimate rights?