Battle of Guamani River Bridge
On August 6, Colonel Coit sent two companies of the 4th Ohio on a reconnaissance mission across and beyond a cast iron bridge that crossed the Río Guanamí (Guamani River). The road beyond the bridge was essential for General Hains' projected advance to the town of Cayey. The 4th Ohio observed elements of Spain's 6th Provisional Battalion entrenched in Guanamí Heights, six miles north of the bridge. The 4th felt that they were too strongly entrenched to attempt an assault at the time. The 4th Ohio requested reinforcements and on August 9, attacked the Spaniards and a short firefight erupted. The numerical superiority of the Americans forced the Spanish to retreat from Guanami Heights. This battle was the costliest battle yet for the Americans since their landing at Guanica, as it resulted in seven wounded. The Spanish forces suffered 2 dead and 15 wounded.
Following the capture of Guayama, the northwestern advance of Peter Hains' brigade was on August 9 contested by the Spanish.
Nearing the Guamani River, the American vanguard came under fire from elements of Spain's 6th Provisional Battalion. A short firefight erupted, in which American numerical superiority forced the Spanish back across the Guamani River bridge.