Russia’s invasion of its neighbor in Ukraine is the largest conventional military attack that’s been seen since World War II, a senior US defense official said Thursday outlining US observations of the unfolding conflict.

“We haven’t seen a conventional move like this, nation-state to nation-state, since World War II, certainly nothing on this size and scope and scale,” the official told reporters Thursday. “And if it unfolds the way that hereto we have come to believe that it will, it has every potential to be very bloody, very costly and very impactful on European security writ large, perhaps for a long, long time to come.”

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