Subsequently, seven other chiefs on seven other islands signed a treaty in German and Marshallese and a final copy witnessed by Rötger on November 1 was sent to the German Foreign Office. The Germans erected a sign declaring a "Imperial German Protectorate" at Jaluit. It has been speculated that the crisis over the Carolines with Spain, which almost provoked a war, was in fact "a feint to cover the acquisition of the Marshall Islands", which went almost unnoticed at the time, despite the islands being the largest source of <answer>copra</answer> in Micronesia. Spain sold the islands to Germany in 1884 through papal mediation.
What notable resource was available in the Marshall Islands?
copra