Why Europe’s current nuclear deterrents may not be enough to face the biggest threat since WWII

Donald Trump shakes hand with Russian President Vladimir Putin during a press conference in Helsinki, Finland, in 2018. Trump this year said he would encourage Russia to do 'whatever the hell they want' to any Nato member country that doesn't meet spending guidelines on defence.
Though a second Donald Trump presidency is not a foregone conclusion, Nato members are gearing up to Trump-proof the organisation and reviewing their defence strategies.
Nato’s concerns about Trump’s re-election were heightened by his flippant comment in February that he would encourage Russia to do whatever it wanted, if certain countries didn’t pay up, defying Nato’s principle that an attack on one constituted an attack on all.