This article carries forward the analysis of militarism begun in IDS Bulletin Vol 8 No 3. It examines the difficult problems of ensuring peace when pressures for military expansion are sustained both by internal class conflict and by international rivalry. The military's interstitial position between the nation State and the international system means that it plays a critical role in reproducing the national class structure and transmitting international influences to Third World countries. It tends to reinforce authoritarian government nationally and great power dominance internationally, although potential for change is created by struggles within military bureaucracies.