What was the cause of tension between the Protestants and Catholics in Northern Ireland during the 1960s

The original conflict between the Catholics and Protestants in Ireland was not a matter of religion, it was a matter of social class.

The cause of tension between the Protestants and Catholics in Northern Ireland during the 1960s was that Catholics wanted to join the Republic of Ireland and the Protestants wanted to stay within Great Britain.

Explanation:

The establishment of Northern Ireland as a political entity produced opposing visions between Catholics and Protestants. To Eamon de Valera's claim that Ireland was a Catholic country, the Northern Irish Prime Minister, James Craig, responded by stating that in Northern Ireland there was "a Protestant parliament for a Protestant population." The differences within Northern Ireland were even more pronounced. The Unionists saw the Catholic minority as inherently disloyal to Northern Ireland, thus justifying preferential treatment for the Unionists. The relative economic success of Northern Ireland against its southern neighbor was used as an argument to claim the existence of Northern Ireland as it was. Catholics, however, had a different view altogether, and believed that the marginalization to which they were subjected was a clear sign that Northern Ireland was an unjust imposition of the United Kingdom in collusion with Protestants.

After the end of the first Irish conflicts in the early 1920s, there were small outbreaks of violence in Northern Ireland through the IRA campaigns between 1942-1944 and 1956-1962, without the support of the population in any of the two sides of the border. However, in response to these attacks, and in anticipation of a new IRA campaign before the 50th anniversary of the Easter Rising, a group of loyalists formed a paramilitary group, the Ulster Volunteer Force.

Towards the end of the 1960s, the situation of Catholics in Northern Ireland led them to organize themselves in the Northern Ireland Civil Rights Association. The confrontation of the Catholic and Northern Irish nationalist minority, organized for the first time on the soil of Northern Ireland, with the Protestant and Unionist majority, would begin the modern conflict of Northern Ireland.