special relationship

noun3

1. •
   A political and diplomatic relationship between two countries that is particularly close and is considered to be based on deep historical and ideological ties rather than merely common interests.
2. •
   The relationship between the United States and the United Kingdom since World War II.

   • Very satisfactory indeed. We got what we came for, and our special relationship is still very special. — 2003
3. •
   The relationship between the United States and Israel since the 1960s.

   • Mearsheimer and Walt argue that the special relationship is in neither nation’s best interest, as the lobby prevents America being an honest broker in resolving Middle East conflict [...]. — 2018