qnli question: What was the Fifth Phase of the Chinese counter initiative called? sentence: The offensive's first thrust fell upon I Corps, which fiercely resisted in the Battle of the Imjin River (22–25 April 1951) and the Battle of Kapyong (22–25 April 1951), blunting the impetus of the offensive, which was halted at the "No-name Line" north of Seoul.