And the pressure to clarify what exactly is happening to Christians and other minorities in the Middle East is certain to intensify in the New Year.

Holocaust Museum said ISIS has carried out genocide against the Yazidis, but its investigation did not cover Christian persecution. Now there's concern the U.S. State Department might do the same, limiting any genocide pronouncement to Yazidis without mentioning Christians.

The letter writers span the spectrum from left to right. Members say they don't want this to become a partisan political issue. In fact, there are reasons administration officials have been cautious in making a genocide declaration.

As Cuba's leader, Castro answered to no one and allowed no challenge to his authority.

Administration officials, in fact, have repeatedly condemned ISIS for its treatment of religious minorities, including Christians. But a bipartisan resolution now moving through Congress calls on the administration to go further and say ISIS is guilty of genocide.

A similar move is underway in the British Parliament. Earlier this month, more than 30 religious leaders and scholars wrote Secretary of State John Kerry asking for a meeting to discuss what's happening to Christians and other minorities. Nina Shea organized the effort.

At one congressional hearing, Bishop Francis Kalabat complained that administration officials are overlooking what's happening to his fellow Chaldean Christians.