 On 3 August 1941, Berryman became Brigadier, General Staff (chief of staff) of I Corps under Lieutenant General John Lavarack, again in succession to Rowell, who became Deputy Chief of the General Staff (DCGS). Berryman arrived in Jakarta by air with the advanced party of the I Corps headquarters staff on 26 January 1942 to plan its defence. Berryman reconnoitred Java and prepared an appreciation of the situation. Berryman also attempted to find out as much as possible about Japanese tactics through interviewing Colonel Ian MacAlister Stewart. This information found its way into papers circulated throughout the Army in Australia. It soon became apparent that the situation was hopeless and any troops committed to the defence of Java would be lost.
