Nonetheless, improved gunpowder artillery played a part in the reconquest of Ireland in the 1530s, where the successful English siege of Maynooth Castle in 1530 demonstrated the power of the new siege guns. There were still relatively few guns in Ireland however and, during the Nine Years' War at the end of the century, the Irish were proved relatively unskilled in siege warfare with artillery used mainly by the English. In both Ireland and Scotland the challenge was how to transport artillery pieces to castle sieges; the poor state of Scottish roads required expensive trains of pack horses, which only the king could afford, and in Ireland the river network had to be frequently used to transport the weapons inland. In these circumstances older castles could frequently remain viable defensive features, although the siege of Cahir Castle in 1599 and the attack on Dunyvaig Castle on Islay in 1614 proved that if artillery could be brought to bear, previously impregnable castle walls might fall relatively quickly.