 Meanwhile , the 1st Battalion , 21st Infantry back at Chonui remained understrength . Half of the force had constituted Task Force Smith at Osan . B and C Companies were thus still refitting at Chochiwon , leaving A and D Companies to hold the line with a handful of replacements to fill the extra positions . The battalion numbered around 500 men in total . The 1st Battalion emplaced on hills overlooking the south road of Chonui , northwest of Chochiwon and prepared to meet and delay the advancing North Korean forces , while the 3rd Battalion emplaced behind it in reserve . Around 0555 on July 10 , the Americans began to detect North Korean movement through the morning fog . Fifteen minutes after daybreak , a whistle blew , immediately followed by small arms fire on the American positions . American forces at first fired indiscriminately into the fog until the regimental commander , Richard W. Stephens , stopped them . At 0700 the 1st Battalion then came under heavy mortar fire , and A Company on the leftmost ridge was assailed with fire from higher ground by North Korean forces of the 4th Infantry Division . The American forces began using 4 @.@ 2 @-@ inch mortars on the North Korean positions in order to prevent them from advancing directly on their positions . Around 0800 the fog began to lift , and the Americans spotted four T @-@ 34 tanks in the village and subsequently called for another airstrike . 
