Complex sentence: British attention then shifted to Greece, which was under the threat of Axis invasion; while Allied divisions were being diverted from North Africa, the Italians were being reinforced with the German "Afrika Korps" under General Erwin Rommel.
Split into simpler sentences: British attention then shifted to Greece, which was under the threat of Axis invasion. While Allied divisions were being diverted from North Africa, the Italians reinforced their positions and were supported by the arrival of the German "Afrika Korps" under General Erwin Rommel.