In early May 1942, Japan initiated operations to capture Port Moresby by amphibious assault and thus sever communications and supply lines between the United States and Australia. The planned invasion was thwarted when an Allied task force, centered on two American fleet carriers, fought Japanese naval forces to a draw in the Battle of the Coral Sea.
The Second Battle of Kharkov or Operation Fredericus was a successful Axis counter-offensive in the region around Kharkov. Operation Fredericus took place from 12 to 28 May 1942. The battle was an overwhelming German victory.
After the Doolittle Raid, the Imperial Japanese Army conducted a massive sweep through Zhejiang and Jiangxi of China, now known as the Zhejiang-Jiangxi Campaign, with the goal of finding the surviving American airmen, applying retribution on the Chinese who aided them and destroying air bases. The operation started May 15, 1942, with 40 infantry battalions and 15–16 artillery battalions but was repelled by Chinese forces in September.
In mid-May, Japan started the Zhejiang-Jiangxi Campaign, which lasted from 15 May to 4 September in China, with the goal of inflicting retribution on the Chinese who aided the surviving American airmen in the Doolittle Raid.
On 20 May, the Soviet Foreign Affairs minister, Vyacheslav Molotov, arrived in London and stayed until the 28th before going on to Washington. The purpose of this visit was to sign a treaty of friendship but Molotov wanted it done on the basis of certain territorial concessions re Poland and the Baltic States. Churchill and Eden worked for a compromise and eventually a twenty-year treaty was formalized but with the question of frontiers placed on hold. Molotov was also seeking a Second Front in Europe but all Churchill could do was confirm that preparations were in progress and make no promises on a date.
The Battle of Gazala was fought during the Western Desert Campaign, west of the port of Tobruk in Libya, from 26 May to 21 June 1942. As both sides neared exhaustion, the Eighth Army checked the Axis advance at the First Battle of El Alamein. To support the Axis advance into Egypt, the planned attack on Malta (Operation Herkules) was postponed. The British were able to revive Malta as a base for attacks on Axis convoys to Libya, greatly complicating Axis supply difficulties at El Alamein.