Complex sentence: He drew the inference that Army HQ had given up hope of holding the Tobruk corridor and signalled mid-morning that without the South Africans his position would be untenable and that he was planning a withdrawal.
Split into simpler sentences: He drew the inference that Army HQ had given up hope of holding the Tobruk corridor. Freyberg signalled mid-morning, that without the South Africans his position would be untenable and that he was planning a withdrawal.