In 1942 the British attempted to re-enter Burma along the coastal region of Arakan. By March the offensive had collapsed, with troops suffering from sickness and low morale. In April 1943 the Japanese launched a counter-offensive that forced the British back to their original positions of six months earlier.
In Arakan in early 1944 the British and Japanese were readying themselves for attack. The British struck first and made gains but were soon hit by the Japanese spoiling attack. The Japanese battled unproductively while the British were supplied from the air and secured in defensive perimeters. Eventually the Japanese gave up and withdrew.
The British, under General Slim, anticipated a major Japanese attack in the north designed to capture the area between Imphal and Kohima (the area needed to launch a future offensive into upper Burma). The British concentrated on the Imphal plain, and using a highly aggressive defence, managed to hold off fierce Japanese assaults. The British also managed to hold off the Japanese at Kohima after severe close-quarter fighting, and by July the Japanese had been defeated. The time was now ripe for the final drive to liberate Burma.
At the start of 1945 in Burma, Slim's 14th Army carried out a bold attack that split the Japanese forces. Following an amphibious assault on Rangoon, the Burma campaign was effectively at an end by May 1945.
While the British had been rebuilding their army on the borders of Burma in 1943 and 1944, the Americans had continued with their island-hopping strategy. After capturing the Gilbert Islands, the Americans prepared to assault the Marshall Islands from where they planned to launch B29 bombers to attack Japanese home islands. On 31 January 1944 the offensive began. The massive and well-executed American attack crushed Japanese resistance in a matter of days. Saipan fell to American forces in June but the length of time taken to capture Leyte in the Philippines delayed the rest of the advance.
In early 1945 the B29 force completed its move to bases in the Marianas and was ready to start a massive aerial attack on Japan. The successful attack on the Bonin Islands, notably Iwo Jima, provided a base closer than those around Saipan. In March 1945 the first deliberate attempt to cause massive fires using incendiaries was mounted. Starting with Tokyo, city after city was attacked. The resulting fires caused huge death tolls and damage - 100,000 died in the first incendiary raid on Tokyo alone.
The last stage of the plan to seize positions suitable for the invasion of Japan was the attack on Okinawa. The Okinawa offensive started on 1 April 1945 and fighting continued until mid-June. The attack was victorious. The only question that remained was how to invade Japan.