The defences of tower houses were primarily aimed to provide protection against smaller raiding parties and were not intended to put up significant opposition to an organised military assault, leading historian Stuart Reid to characterise them as "defensible rather than defensive". Gunports for heavier guns were built into some Scottish tower houses by the 16th century but it was more common to use lighter gunpowder weapons, such as muskets, to defend Scottish tower houses. Unlike Scotland, Irish tower houses were only defended with relatively light handguns and frequently reused older arrowloops, rather than more modern designs, to save money.