The UK will spend 2.5 per cent of its income on defence by the end of the decade, Boris Johnson says.
The US announces a new permanent base in Poland – while Sweden and Finland are formally invited into the Nato military alliance.
The foreign secretary said she feared Vladimir Putin had been emboldened by lacklustre defence and deterrence.
He claimed the Russian president would not have invaded Ukraine if he were a woman.
Ben Wallace also compared the situation in Ukraine to the Nazi invasion of Poland in 1939.
Plea comes as the prime minister ditches Tory manifesto pledge to boost the armed forces budget.
"In these days of long range missiles and stealth - distance is no protection," the cabinet minister said.
It's starting to look like Ukraine might not be able to win on its own – and Russia certainly isn't going to give up.
General Sir Patrick Sanders says he has never seen such a clear threat to peace and democracy as the “brutal aggression” of Russian president Vladimir Putin.