'Puran 21' was a Japanese unrealised plan by Lieutenant General Shojiro Iida’s 15^th Army for an invasion of Assam in north-eastern India from western Burma (autumn/23 December 1942).

The object of this offensive would have been to capitalise on the Japanese successes in 'B' (iii) before the end of the campaign as the 1942 spring monsoon broke, by advancing into Assam against British and Indian forces still trying to reorganise themselves after their losses in the Burma campaign.

'Puran 21' called for Lieutenant General Shozo Sakura’s 33^rd Division to advance from Kalewa to take Dimapur and Silchar, Lieutenant General Renya Mutaguchi’s 18^th Division (reorganised as a mechanised formation) then to pass through the 33^rd Division to deal with any counterattack and take Golaghat, and a detachment of the 18^th Division to advance up the Hukawng valley to take Ledo and thus shield the right flank of the operation.

The plan was cancelled on 23 December 1942.