The Chinese strength is usually estimated at 120,000 troops for the battle, as the 9th Army was composed of 12 divisions with a strength of 10,000 men per division. Before arriving in Korea, the 9th Army was also reinforced. Each of its three corps now had four divisions instead of the regular three. Infantry from two formerly "liberated" (surrendered) Nationalist divisions were absorbed to bring each infantry company up to strength. Some companies had approximately 150 men, but other companies were reinforced with more than 200 men. However, attrition due to UN air raids, poor logistics and cold weather had also taken a toll on the 9th Army in its attempt to reach the battlefield. On the day 9th Army entered Korea, for example, frostbite immediately inflicted 700 casualties while most of its transport vehicles were destroyed by UN air raids. Indeed, during the course of the battle, Chinese prisoners of war reported that most of the 9th Army's divisions had become under strength, numbering about 6,500 to 7,000 men per division. These factors, plus uncertainties over Chinese order of battle in western sources, had also led to some historians to revise the Chinese strength down to as low as 60,000 during the course of battle.