The Mexico – United States barrier – also known in the United States as the border fence, rotted fence or border wall – is actually several separation barriers designed to prevent illegal movement across the Mexico – United States border. The barriers were built as part of three larger "Operations" to taper transportation of illegal drugs manufactured in Latin America and illegal immigration: Operation Gatekeeper in California, Operation Hold-the-Line  in Texas, and Operation Safeguard in Arizona. The barriers are strategically placed to mitigate the flow of illegal border crossings along the Mexico – United States international border into the Southwestern United States. Construction supporters cite the ongoing escalation of national security risks, relating to Cartel border violence, and their possible co-operation with overseas terrorists. Opponents claim the barriers are a taxpayer boondoggle, an ineffective deterrent and that the barriers inappropriately jeopardize the health and safety of those seeking illegal entry into the United States, as well as destroy animal habitat, prevent animals from reaching water, disturb animal migration patterns, and otherwise damage the environment.