Americans have gone abroad on their own to fight for many causes during our nation's history.
Daring American airmen joined the Lafayette Escadrille to fight Germans before the United States entered World War I. Long before Pearl Harbor, others battled the Japanese as members of the "Flying Tigers."
None of them used knives to cut off the heads of noncombatants, however.
The murder this week of an American reporter captured by Islamic State terrorists in Syria has focused new attention on "foreign fighters" in such groups.
James Foley's brutal execution was videotaped and distributed worldwide by the terrorists. There followed a sequel showing the execution of journalist Stephen Sotloff. The man shown using a knife to decapitate Foley is believed to be a British citizen.
Officials in that country have mounted a campaign to identify British residents who may sympathize with Islamic terrorists, in an effort to keep them from going abroad to join the groups. Other countries, including France, are taking similar action.
What about the United States? It is known some Americans have joined terrorist groups and even become leaders in them. Yet U.S. officials from President Barack Obama on down have said little about efforts to keep that from happening.
No one getting on an airplane to leave the United States proclaims he is off to become a murderous jihadist. Identifying and stopping such potential recruits is difficult. Still, U.S. officials should be doing all in their power to do that, even as they work to prevent domestic terrorism.