Article 42.7 had languished in obscurity for decades – until Donald Trump began casting doubt on US commitment to Nato • Don’t get This Is Europe delivered to your inbox? Sign up here Most people have heard of Nato’s article 5 . The “one for all, all for one” clause states an armed attack on one member country should be considered an attack on all, requiring member states to come to the victim’s aid – including with “the use of armed force”. Not so many, till this week, had heard of the EU’s own mutual defence clause, article 42.7 (pdf) , which says that if a member state comes under armed attack, the others “shall have towards it an obligation of aid and assistance by all the means in their power”. That’s perhaps because there hadn’t, until recently, been much need for Europeans to consul