The name by which the series of acts passed between 1536 and 1543, during the reign of Henry VIII and dealing with the nature of government in Wales are generally known. They were not, however called "Acts of Union" at the time, and in fact it was not until 1901 that this title was bestowed upon them by Owen M Edwards, but the name has tended to stick. Indeed the name "Acts of Union" is something of a misnomer; it invites comparison with those other Acts of Union of 1707 and 1801 which are quite a different matter altogether.
In this case it was not a question of uniting two countries together as Wales had already been effectively incorporated into England since the days of the Statute of Rhuddlan in 1284. A fact which the preamble to the act of 1536 makes clear, stating (on behalf of the king) that Wales "is and ever has been incorporated, united and annexed to and with his Realm of England"; somewhat of an exaggeration, but in essence the simple truth.
What the Acts really united was Wales itself, sweeping away a hotch-potch of direct royal rule and semi-independent marcher lordships and creating a unified administrative system across the whole of the nation.
The Background to the Acts
Henry VIII had ambitions for his kingdom and these Acts were part of the process , sometimes called the Tudor Revolution, engineered by one Thomas Cromwell by which he ensured the exercise of royal sovereignty throughout the kingdom.
In addition of course, Henry VIII had engineered his split with Rome and placed himself at the head of the new Church of England. A move that was not universally popular, particularly in a conservative place such as Wales. And Wales had a certain strategic importance, both as a possible invasion route for the catholic powers of France or Spain and secondly (and more importantly perhaps) because Wales controlled the main lines of communication with Ireland.
The Welsh gentry had been petitioning for change for many years (they wanted the same opportunities to accumulate land and get rich as their English brethren). By bringing the administration of Wales into line with that of England and thereby offering the Welsh ruling class the same opportunities for advancement Henry VIII could therefore be reasonably certain of their reciprocal support.
The main provisions of the Acts
Administration: the division of Wales into a system of administrative counties and the provision of parliamentary representation; the so-called Shiring of Wales. As a result the marcher lordships, so long an anomalous feature of the Welsh political landscape were abolished.
Statutory recognition was also given to the Council of Wales and the Marches which had jurisdiction over both Wales (in the sense of the thirteen counties) and the four border counties of England.
Law: It provided the Welsh with equality under the law with the English, ended the use of the law of Hywel Dda in matters of land tenure and established the English system of common law throughout the country to be administered and enforced by the Courts of Great Sessions.
Language:That English would be the only language used in the courts and that no one able to speak to Welsh would be permitted to hold office unless they also had command of the English language.
Consequences of the Acts
From the point of view of the gentry the Acts were unequivocally a 'good thing'; freed from the constraints of traditional Welsh land tenure they could build up their estates, they could take up office within the local administration, seek election to parliament and generally follow the pursuit of wealth and power in a similar manner to their English brethren.
In more modern times the Acts have come under greater criticism, the language clauses in particular seen as an example of English cultural imperialism.
It was not the specific intention of government to discourage the use of the Welsh language, the objective was rather one of uniform administration, but what the language clauses did provide was a reason and a stimulus for the Welsh gentry to learn English in order to qualify for office. By this process, over the succeeding generations the Welsh ruling class became anglicized and therefore divorced from the people of Wales. This was to have profound consequences on the future development of Welsh culture.
SOURCE A History of Wales by John Davies