Original sentence: The offensive's first thrust fell upon the multinational units of US I Corps, which resisted at the Battle of the Imjin River and the Battle of Kapyong which took place at the same time over the period 22–25 April 1951, blunting the impetus of the offensive, which was halted at the "No-name Line" north of Seoul
Edited sentence: The offensive's first thrust fell upon the multinational units of US I Corps, which fiercely resisted at the Battle of the Imjin River and the Battle of Kapyong which took place at the same time over the period 22–25 April 1951, blunting the impetus of the offensive, which was halted at the "No-name Line" north of Seoul