Complex sentence: When Lord Rawlinson died in March 1925, he acted temporarily as Commander-in-Chief, India, until Sir William Birdwood took over that role and Jacob returned home again to take up the appointment of Military Secretary to the India Office.
Split into simpler sentences: When Lord Rawlinson died in March 1925, he acted temporarily as Commander-in-Chief, India. When Sir William Birdwood took over that role, Jacob returned home again to take up the appointment of Military Secretary to the India Office.