By capturing Burma in May 1942 the Japanese achieved the planned limit of their westward exploitation, at least for the time being. Throughout the remainder of that year and most of 1943 they were content to consolidate and defend their gains, and it was not until late 1943 that they began to probe further in any strength. The allies were not to know that at the time, of course, and, with Burma lost, a Japanese attack on Assam or east Bengal after the 1942 monsoon appeared to be a distinct possibility. Operational thinking in GHQ(I) and the Eastern Army in early 1942 was focused, therefore, on the urgent deployment, training and maintenance of forces sufficient to prevent any further advance. Once an adequate defensive posture had been achieved, attention could turn to the possibility of building up sufficient strength for offensive operations, but that was destined to be a long, drawn-out process. The most pressing logistic concerns at the operational level during 1942 and 1943 surrounded the capacity of the poor quality, overstretched overland LofC between the developing strategic base in India and the two corps fighting at the tactical level. There were two distinct but linked corridors of communication. The river, road and rail routes following the general line of the Brahmaputra from Calcutta to north-east Assam were known as the Assam LofC or the ‘northern line’. Those to Chittagong were known as the east Bengal LofC or the ‘southern line’ (see Map 3). In addition to British operations in Assam, the northern line also had to sustain what rapidly became the allied strategic main point of effort in the South-East Asia theatre: the American-led operations to maintain and expand the link to China. Under the prevailing environmental and economic conditions, these were immense undertakings. Like the India base, the LofC were incapable of supporting the level of activity envisaged by the Combined COS in the time frames at first desired. It was not until monumental difficulties had been overcome that the China airlift could achieve the rate of delivery promised by the Americans, or any major offensive to open a new overland route could even be considered.