ABSTRACT
The massive German ‘Michael’ offensive of 21 March 1918 (Map 3.1) was expected by the BEF, but the nature of the German offensive caught the BEF by surprise. In a matter of hours the command structure of the BEF began to break down, and continued to do so for the next six or seven days. But the underlying reason for the rapid retreat of the BEF’s Fifth and Third Armies was the failure to understand and properly apply the new three-zone, defence in depth system, copied from the German army. As a result, Fifth and Third Armies separated, and more seriously, Fifth Army separated from the neighbouring French army, leading to a hitherto misunderstood disagreement between Haig and Pétain. During the BEF’s retreat, three major events help explain how GHQ and the BEF command structure lost control: the initial German breakthroughs of 21 and 22 March (which will be followed through the fortunes of just two divisions, 16 and 47); the tardy evacuation of the Flesquières or Cambrai salient by Third Army on 22 and 23 March; and the hasty retirement of Fifth Army behind the line of the Somme from 22 to 25 March. Further problems also occurred with the BEF’s artillery and air arms. But the innovative German stormtroop tactics were not sufficiently maintained either, and German casualties mounted when traditional mass tactics were used. All in all, however, the keynote of the BEF retreat was the collapse of the command structure, and the inability of the army to comprehend, build and properly employ, the new defence in depth system.
