The little-known clause that Europe’s security may now depend on

M ost 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 …