‘We have no eternal allies, and we have no perpetual enemies. Our interests are eternal and perpetual, and those interests it is our duty to follow’. These famous words were uttered by Lord Palmerston, later British prime minister, in 1848. They capture the core argument of realist alliance theory: that states ultimately choose their cooperation partners for strategic purposes, that other states can never be fully trusted and that alliances between states must therefore be expected to occur only infrequently – in periods where strategic interests happen to coincide. Within such a framework, the prospects of long-term alliances between states seem unlikely, and the formation of genuine friendships even less so.