 Most significantly, he stationed a troop of M113s from the 1st Squadron, 1st Cavalry, at Ross, giving the base a hard-hitting reaction force.Koster learned more about the 2nd Division's plans on 9 December, when his main air reconnaissance element, Troop B of the 1/9th Cavalry, spotted a battalion-size group of PAVN 5km northwest of LZ Baldy.After air and artillery strikes had pounded the location, several companies from the 1/35th Infantry, moved in to engage the PAVN.