Conflicts of high intensity and lengthy duration may have to rely mostly on supplies that are produced while they are ongoing.[1] The first and second World Wars provide examples of this.[citation needed] But smaller wars of shorter duration where belligerents have already stockpiled sufficiently for the outbreak of conflict are able to rely on pre-existing stock. The U.S. Invasion of Grenada (1983) or Panama in 1989, in particular, were small enough to be almost wholly reliant on existing stock.[citation needed]