A Turkish attack on northern Iraq to end cross-border raids by the rebel Kurdistan Workers’ Party (PKK) is beginning to look politically unstoppable after this weekend’s attack on troops in south-east Turkey, the worst in a decade.

Recep Tayyip Erdogan, the prime minister, is under intolerable pressure that will test his skill and judgment to the limit. The PKK attacks have outraged Turks, emboldened the electorally defeated ultranationalists and put Turkey’s powerful army back on the front foot after a string of setbacks in its cold war with Mr Erdogan’s neo-Islamist Justice and Development party.