The term "internationalised armed conflict" describes internal hostilities that are rendered international, such as war involving a foreign intervention in support of an insurgent group fighting against an established government.
Some scholars also use the term “internationalised armed conflict”, for Non-International Armed Conflicts with an international dimension, which are legally in between internal and International Armed Conflicts. The term describes internal hostilities that are rendered international. The factual circumstances that can achieve that internationalisation are numerous and often complex: the term internationalised armed conflict includes…war involving a foreign intervention in support of an insurgent group fighting against an established government. However, the Manual on the law of Non-International Armed Conflict disregards this definition and stresses that an armed conflict has to be either internal or international:
When a foreign State extends its military support to the government of a State within which a Non-International Armed Conflict is taking place, the conflict remains non-international in character. Conversely, should a foreign State extend military support to an armed group acting against the government, the conflict will become international in character.
DISCUSSION PAPER 2: DRONE ATTACKS, INTERNATIONAL LAW, AND THE RECORDING OF CIVILIAN CASUALTIES OF ARMED CONFLICT, p. 8