Complex sentence: When World war II loomed, the size of the Territorial Army was doubled, and the role of the QOOH changed again, becoming the 63rd (Oxfordshire Yeomanry) Anti-Tank Regiment.
Split into simpler sentences: When World war II loomed, the size of the Territorial Army was doubled, and the role of the QOOH changed again. It was changed to the 63rd (Oxfordshire Yeomanry) Anti-Tank Regiment.