 The battle was also noted for the pioneering use of tunnel warfare by the Chinese in the Korean War . During the fighting , a company of Chinese soldiers had defended their positions from a U @-@ shaped tunnel capable of housing 100 men , which had served as both a bomb shelter and a base for counterattacks . The company leader later claimed that the tunnel enabled the defenders to inflict 700 UN casualties while suffering only 21 casualties in return . Impressed by the report , the commander of the People 's Volunteer Army , Peng Dehuai , later ordered the construction of 30 @-@ metre ( 98 ft ) deep tunnels along the entire front line , and it formed a formidable obstacle for UN forces to overcome during the stalemate period . 
 The battle was also noted for the pioneering use of tunnel warfare by the Chinese in the Korean War . During the fighting , a company of Chinese soldiers <a href='been_done' title='1'><mark>had</mark></a> defended their positions from a U @-@ shaped tunnel capable of housing 100 men , which <a href='been_done' title='2'><mark>had</mark></a> served as both a bomb shelter and a base for counterattacks . The company leader later claimed that the tunnel enabled the defenders to inflict 700 UN casualties while suffering only 21 casualties in return . Impressed by the report , the commander of the People <a href='null_genetive' title='3'><mark>'s</mark></a>Volunteer Army , Peng Dehuai , later ordered the construction of 30 @-@ metre ( 98 ft ) deep tunnels along the entire front line , and it formed a formidable obstacle for UN forces to overcome during the stalemate period . 
The battle was also noted fa da pioneering use of tunnel warfare by tdaChinese in thdaorean War . durin the fighting , a company of Chinese soldiers done defended their positions from a U @-@ shaped tunnel capable of housing 100 men , which done served as both a bomb shelter and a base for counterattacks . The company leader later claimed that thedannel enabled the defenders to inflict 700 UN casualties while suffering only 21 casualties in return . Impressed by the report , the commander of the daple  Volunteer Army , Peng Dehuai , later ordered the construction of 30 @-@ metre ( 98 ft ) deep tunnels along the entire front line , and it formed a formidable obstacle ffirUN forces to overcome ddurinthe stalemate period .