The Mediterranean and North Africa played a key role in WW2, especially in the earlier stages.
North Africa contained important reserves of oil. Egypt was also a crucial British territory. If Hitler or his ally Mussolini, leader of Italy, captured Egypt then they could threaten British naval bases in the Mediterranean. They could also threaten the Suez Canal. This was a vital communications link for troops and resources from India and other parts of the British Empire.
The first major developments came in September 1940 when Italian forces from Libya (which was controlled by Italy) invaded Egypt.
British Empire forces in Egypt drove the Italians back by the end of 1940, driving deep into Libya and capturing the port of Tobruk.
Dismayed by the British successes, Hitler sent German forces, Afrika Korps, under General Rommel to help his Italian allies. Rommel pushed British forces back to Egypt in April 1941, but for the rest of that year the two sides were unable to gain a decisive advantage.
Meanwhile, there were important developments in the Mediterranean area. German and Italian forces bombarded the British run island of Malta but failed to force the British out. The civilian population of the island were awarded a George Cross. In April and May of 1941 German and Italian forces conquered Yugoslavia and Greece. Crete fell in May 1941.
In 1942 Rommel achieved a series of impressive victories against the British. He captured Tobruk in May 1942 and pushed deep into Egypt. By July 1942 he had reached El Alamein. Desperate resistance from British Empire forces forced him to halt here. In August 1942 the British 8th army got a new commander, General Montgomery. He reorganised British Empire forces and attacked Rommel in October 1942, achieving a decisive victory.
From this point on Rommel was pushed back.
In November 1942 British Empire and American forces landed in the western corner of North Africa in Operation Torch. Montgomery continued to push from the East. By May 1943 Rommel's forces had been defeated.
The next key stage in the campaign was mainland Europe. In July 1943 Allied forces invaded Sicily. Sicily fell in August. The 8th Army then landed in Italy in September 1943 and the Italian government surrendered soon after. However, German forces in Italy kept fighting. The Italian campaign became a long, hard slog with many bloody battles such as Monte Cassino in January 1944. Rome was finally taken in June 1944 but the German resistance in Italy continued until May 1945.