unmask one's batteries

From the revealing of artillery previously concealed from the enemy’s line of sight, immediately before opening fire.

• "“Your father is fond of surprises, as you must have seen,” Cuthbert rejoined. “He won’t unmask his batteries till all is ready for action.”"
• "The bishops, proud of this first victory, believed that a second would be easily won, and they unmasked their batteries."
• "The Evénément^([sic]) remarks:—“The Egyptian Question is not a French or an Anglo-French, but a European question, and the spoliation just perpetrated by England, has enlightened Europe in time. It is not wise to unmask one’s batteries too soon.”"
• "Meanwhile the Germans had shown that they themselves were not yet ready to unmask their batteries."