Obama drew a red line and told Putin not to cross it. Putin crossed the line Obama did nothing. Maybe he hid under his desk and whenever the phone rang he'd say "if that's Putin calling just tell him I'm in the shower."

“When President Obama declared Friday that ‘there will be costs’ for any Russian intervention in Ukraine,” Marc Thiessen, the former George W. Bush speechwriter and American Enterprise Institute fellow, wrote in 2014, “you could hear the laughter emanating from the Kremlin—followed by the sound of Russian military vehicles roaring into Crimea and seizing control of the peninsula. ‘Costs?’