"Monadnock" departed on 5 October in company with the paddle frigates and and the sloop . The monitor steamed the entire way to California entirely under her own speed and the biggest problem reported was that temperatures in the fire room ranged from . Stokers collapsed daily from heat prostration and special inducements of extra pay and spirits had to be offered for men to take their place. After stops at numerous South American ports, the squadron transited the Strait of Magellan and arrived at Valparaíso in late March 1866 as a Spanish squadron was preparing to bombard the undefended town, contrary to international law, during the Chincha Islands War. Commodore John Rogers, commander of the American squadron, attempted to persuade Admiral Casto Méndez Núñez to forego the bombardment, but the latter claimed it was a point of Spanish honor. Rogers even had his ships clear for action in an unsuccessful attempt to intimidate Méndez Núñez and was prepared to open fire if he received support from the small British squadron in the harbor. That was not forthcoming as the British minister in the town forbade Rear-Admiral Joseph Denham to act and Rogers was forced to stand down.