Regional experts also predicted that Russia may look to take advantage of the uncertainty created by James Mattis's resignation as President Trump's defense secretary.
https://www.newsweek.com/ukraine-russia-war-attack-christmas-1270621
https://www.gazeta.ru/army/2018/12/24/12106177.shtml
https://www.gazeta.ru/politics/2018/12/24_a_12106369.shtml
https://www.gazeta.ru/business/2018/12/24/12106885.shtml?updated
https://www.rbc.ru/newspaper/2018/12/24/5c1cb12c9a794754db2482c5
https://www.kommersant.ru/doc/3841692
http://www.kasparov.ru/material.php?id=5C20BC4282C5D
https://newtimes.ru/articles/detail/175201
https://newtimes.ru/articles/detail/175194