The outbreak of war in September 1939 found the 1st Devons at Rawalpindi in India, training to become a machine gun battalion. In April 1940 they moved to Abbotabad to train in mountain warfare before in September being posted to the North West Frontier near Razmak. Here, trying to keep open the frontier roads, they were often in action against the local tribesemen. In the New Year, after a Christmas involving another skirmish with Waziris, they moved to the Rizani sector to continue similar operations.
In April 1941 the Battalion were moved to Jullundur to train for desert warfare as they expected to go to North Africa. After the Japanese invasion of Burma they were instead prepared to go to Burma to defend Rangoon. When, before they had embarked, Rangoon fell, they were moved to Lahore, Secunderabad and Ceylon (now Sri Lanka). After jungle training and joining 20th Indian Division, the 1st Devons finally reached Burma in the late summer of 1943.
By October 1943 the Battalion were in action near Tamu, patrolling the Kabaw Valley and the line of the River Chindwin until the Japanese offensive began in March 1944. During the next two months the Devons played a notable part in defending the hills along the Tamu road, which included the notorious Nippon Hill. The Devons’ part in the successful assault on Nippon Hill cost them 20 killed and 67 wounded.
When the Japanese offensive was defeated and General Slim’s Fourteenth Army began to drive their enemy southwards the Devons’ role was to advance up the Iril Valley and cut the Kohima-Ukhrul road behind the retreating Japanese. Here the 1st Devons faced strong enemy resistance as they conducted sweeps through the jungle to remove pockets of resistance. In a series of actions the Battalion lost 13 killed and 37 wounded until the road was cleared for the British advance south. In mid-July they were withdrawn to Imphal to recuperate and prepare for the long advance to Mandalay.
In November 1944 the Battalion rejoined the advance south and excelled in the bitter battles between the River Irrawaddy and Kyaukse, south of Mandalay. One New Year’s Day they crossed the River Chindwin . On 22nd February 1945 they assaulted and captured Kanlan. In early March they fought at Sinbyugan before advancing to and attacking Gyo. Late in March they attacked Letpanpin without success but within two days it was taken and, by 1st April, the Devons were in position below Mandalay astride the road to Rangoon.
In May 1945 the 1st Devons returned to India and were stationed at Visapur, near Poona. Their total losses during the campaign were 122 killed, 307 wounded and 9 men missing. Their eighteen-month campaign won the Regiment seven new battle honours.