North Korea continues along the nuclear path. A new report warns that Pyongyang could amass a nuclear arsenal as large as 100 weapons by 2020. That would make the North a significant regional power.

Washington has no realistic strategy to deal with North Korea. Some policymakers have advocated offensive military action, but that likely would trigger a war which would devastate South Korea.

The Obama administration's chief policy has been to reaffirm Washington's defensive alliance with the South. Some 28,500 U.S. troops are on station, backed by conventional and nuclear forces elsewhere.