Under the Forgáč family the castle grew into a fortress fit for gunpowder: through the fifteenth and sixteenth centuries new palaces went up, and a great trapezoidal tower and a round tower were built to cover the entrance. Somebody had to pay for it. The extra labour service, dues and taxes squeezed out of the villagers below produced a peasant revolt in 1610, which the lords put down harshly. Then the frontier arrived: in the autumn of 1663 the Ottomans took the fortress of Nové Zámky, and their raiding parties reached Gýmeš and wrecked it. The castle was repaired, and the repair is still legible in its plan — a new line of defence with cannon bastions on the exposed southern side.Za Forgáčovcov sa z hradu stala pevnosť pre dobu strelného prachu: v 15. a 16. storočí pribudli nové paláce a pri vstupe veľká veža lichobežníkového pôdorysu aj valcová veža. Niekto to však musel zaplatiť. Zvýšené roboty, poplatky a dane vyústili v roku 1610 do vzbury poddaných z podhradia, ktorú panstvo kruto potlačilo. Potom prišla hranica: na jeseň 1663 Osmani dobyli pevnosť Nové Zámky a ich oddiely sa dostali až ku Gýmešu a zničili ho. Hrad obnovili a oprava je v pôdoryse čitateľná dodnes — na najohrozenejšej južnej strane pribudlo nové opevnenie s delovými baštami.
