The topic of homeland security includes a broad array of missions and mission areas ranging from national missile defense to military assistance to civil authorities. Recently the topic has attracted a great deal of attention due to the public's heightened awareness of the variety and nature of emerging threats and of the United States' vulnerabilities to them. This monograph, written by Lieutenant Colonel Antulio J. Echevarria II, grew out of a tasking by the Army Staff to investigate the Army's role in homeland security from a strategic, rather than a legal or procedural perspective. The author achieves this perspective by placing homeland security missions within the larger spectrum of operations. In so doing, he exposes potential problem areas-missions requiring more or different force structure than that already available-for further action by the Army.