Conflicts of high intensity and lengthy duration may have to rely mostly on supplies that are produced while they are ongoing. The first and second World Wars provide examples of this. 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.