For decades North Korea has threatened to turn enemy cities into a “sea of fire,” even as it doggedly worked on building a nuclear weapons program that could back up its belligerent words.

Now, as North Korea conducts another torrid run of powerful weapons tests — and threatens pre-emptive nuclear strikes on Washington and Seoul — it may be taking inspiration from the fiery rhetoric of the leader of a nuclear-armed member of the U.N. Security Council: Russia’s Vladimir Putin.

With Putin raising the terrifying prospect of using tactical nukes to turn around battleground setbacks in Ukraine, there’s fear that this normalization of nuclear threats is emboldening North Korean leader Kim Jong Un as he puts the finishing touches on his still incomplete nuclear program.

“Putin and Kim feed off each other, routinizing the right to nuke a peaceful neighbor by repeating it without repercussion,” said Sung-Yoon Lee, an expert on North Korea at Tufts University’s Fletcher School of Law and Diplomacy. “Putin’s threats sound more credible than Kim’s, as there is bloodshed in Ukraine every day. But Kim’s threats must not be dismissed as empty bluster.”

After more than 40 missile launches this year — its most ever — there are a host of fresh signs that North Korea is becoming more aggressive in making its nuclear bombs the centerpiece of its military.