has. we're just air raid sirens and people are being told to go into basements. the united nations said half a million refugees have fled ukraine. we crossed over the board fresh poland today and you see women and children at the border going through the lengthy procedures to cross over the border. one mother who escaped romania said she could not hide her fear. she may not be able to return to her homeland. >> it is hard to come back. to come back, i don't know. we're scared about our husbands, our brothers. >> reporter: well cnn is covering the war in europe for all angles. clarissa ward is in kyiv tonight and nic robertson is in moscow. let's start with national security correspondent alex