spike somebody's guns

spike somebody’s ˈguns

(British English) spoil somebody’s plans because you do not want them to succeed: She was jealous of David’s progress in the company, so she spiked his guns by telling the boss that David had a drinking problem.This refers to pushing a metal spike (= a thin object with a sharp point) into the enemy’s gun or cannon so that it cannot be fired.
See also: gun, spike