Praise be to Allaah.
Taking the kaafirs as friends (muwaalaah) means supporting them and helping them in matters of kufr, such as the Muslims fighting alongside the kuffaar, such as when the kaafirs launch an assault against a Muslim country and a Muslim befriends them and supports them and helps them in fighting against that country, whether that is with weapons or by supplying them with anything that will help them to fight the Muslims. This is muwaalaah, or a type of friendship that is haraam,