Why is Crimea critical to the Ukraine war?

Russia annexed Crimea in 2014. Now, more than four years into the current war, Ukraine is targeting the peninsula with increased drone attacks. In response, authorities in the Russian-controlled region have declared a state of emergency, admitting they're facing challenging times. This week, Ukraine's President Volodymyr Zelenskyy announced the start of what he called a 40-day 'influence operation' to push Russia to end the war.