Schools that have not received explicit threats have still taken precautions, such as practicing shooting drills and installing metal detectors. (ibtimes.com)
The court easily characterized the patentee API's letters as «contain [ing] explicit threats of litigation»: (slaw.ca)
With one sad exception (the military incursion in Panama), it has always been defending against explicit threats from entities whose stated goal was world domination. (politics.stackexchange.com)