The Norman invasion of Ireland began between 1166 and 1171, under first Richard de Clare and then Henry II of England, with the occupation of southern and eastern Ireland by a number of Anglo-Norman barons. The rapid Norman success depended on key economic and military advantages, with castles enabling them to control the newly conquered territories. The new lords rapidly built castles to protect their possessions, many of these were motte-and-bailey constructions; in Louth at least 23 of these were built. It remains uncertain how many ringwork castles were built in Ireland by the Anglo-Normans. Other castles, such as Trim and Carrickfergus, were built in stone as the "caput" centres for major barons. Analysis of these stone castles suggests that building in stone was not simply a military decision; indeed, several of the castles contain serious defensive flaws. Instead the designs, including their focus on large stone keeps, were intended both to increase the prestige of the baronial owners and to provide adequate space for the administrative apparatus of the new territories. Unlike in Wales the indigenous Irish lords do not appear to have constructed their own castles in any significant number during the period.