When the administration of then-U.S. President Barack Obama imposed sanctions on Russia for invading Ukraine in 2014, American officials were hopeful they would deter Russian President Vladimir Putin from further aggression.

Some of the officials argue today that the sanctions prevented Putin from ordering Russian forces beyond where they had halted on the Crimean Peninsula and in the eastern Donbas region. But Putin held on to Crimea. And on Monday, he ordered more troops into an insurgent-controlled area of eastern Ukraine where thousands of Russian soldiers have been operating and said the Kremlin was recognizing the enclaves as independent states.

Now, U.S. President Joe Biden, who as vice president helped oversee Ukraine policy in 2014, has to weigh what sanctions might compel Putin to halt his new offensive, which the White House has judged to be an "invasion.” The White House is taking a step-by-step approach, trying to calibrate each tranche of measures to Putin’s actions.