The last bit from the BAS piece that I’ll mention is this reiteration of Trump Administration policy concerning retaliation for a nuclear terrorist attack:

 The 2018 Nuclear Posture Review pointedly warns adversaries that abetting a terrorist nuclear attack against the United States would qualify for “the ultimate form of retaliation,” whose meaning should be unmistakable.

Presumably, they’re referring to this NPR paragraph:

For effective deterrence, the United States will hold fully accountable any state, terrorist group, or other non-state actor that supports or enables terrorist efforts to obtain or employ nuclear devices. Although the role of U.S. nuclear weapons in countering nuclear terrorism is limited, our adversaries must understand that a terrorist nuclear attack against the United States or its allies and partners would qualify as an “extreme circumstance” under which the United States could consider the ultimate form of retaliation.

I’m not sure that I understand the point of the ambiguous language, but there it is.