TADIL-J refers to "Tactical Digital Information Link Joint" (TADIL) which was used by the U.S. Navy, U.S. Army, U.S. Marine Corps, U.S. Air Force, the NSA, several NATO countries, and Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

 as part of the Multi-Tactical Data Link Network (MTN). TADIL-J refers to the system of specialized data radios and specially-formatted messages ("J" series messages) which is the predecessor to the Link 16

Link 16

Link 16 is a military tactical data exchange network created and used by the United States and adopted by some of its Allies and by NATO. Its specification is part of the family of Tactical Data Links....

 system defined by military standard, MIL-STD-6016D.

Other TADILs included TADIL-A, TADIL-B, and TADIL-C whose designations were replaced by Link 11, Link 11B, and Link 4 respectively.

TADIL is no longer an official US Department of Defense term (per DISA

Defense Information Systems Agency

The Defense Information Systems Agency is a United States Department of Defense agency that provides information technology and communications support to the President, Vice President, Secretary of Defense, the military Services, and the Combatant Commands.As part of the Base Realignment and...

 guidance). Instead it has officially been replaced by the generic term Tactical Data Link (TDL). However, the term "TADIL" is a legacy holdover and still used in the vernacular.