In March 1937 General Franco decided to halt his stalling assault on Madrid and redirect his efforts to the Republican-held territory on the Bay of Biscay, containing the city of Bilbao, Spain’s main industrial centre. The Nationalist offensive was led by General Mola and supported by indiscriminate German and Italian bombing of civilian targets in Durango and Guernica. While the Republican defenders had, theoretically, superiority in numbers, the nationalists had vastly superior armaments and, crucially, virtual control of air and sea. Furthermore, the Republican command was riven with dissension between socialist and Basque nationalist elements. A maritime blockade was instituted, and after Italian divisions of the nationalist army captured Bermeo on 30 April, a final assault on Bilbao’s ‘Iron Ring’, a defensive labyrinth of bunkers and tunnels, was ordered. The Ring proved anything but iron: its layout had been betrayed and it was swiftly obliterated by precision bombing. Bilbao fell on 19 June.
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