On December 18, the United States resumed its bombing of North Vietnam after Paris peace negotiations reached an impasse. The campaign was called “the Christmas bombings”.
Richert, Lucas Paul. "Full-scale bombing of North Vietnam". The Literary Encyclopedia. First published 01 November 2008
[http://www.litencyc.com/php/stopics.php?rec=true&UID=5691, accessed 24 May 2013.]