If you are short on time, these resources are your best bet for this topic:
Victory Fever on Guadalcanal by 
First Wave at Los Negros, Admiralty Islands. (DA photograph)
Image downloaded from: https://history.army.mil/brochures/new-guinea/ng.htm
On 2 July 1942 the U. S. Joint Chiefs of Staff ordered Allied forces in the Pacific to mount a limited offensive to halt the Japanese advance toward the line of communications from the United States to Australia and New Zealand. At the same time the United States was committed to a program for building up forces in Great Britain to launch an offensive in Europe in 1942 or 1943. There were then available so few warships, transports, and cargo ships, so few trained troops, so few weapons and supplies, that any offensive in the Pacific, for which the United States would have to provide most of the forces, would necessarily be limited in scale. Yet it was essential to halt the Japanese who were then moving ever nearer to the flank of the tenuous line of communications. The Joint Chiefs' decision of 2 July led to the long, grim struggle for the possession of Guadalcanal, an island in the remote British Solomon Islands Protectorate which was not specifically named in the orders dispatched by the Joint Chiefs.
Source: https://history.army.mil/books/wwii/GuadC/GC-01.htm
