After the Second World War the Home Nations rejoined FIFA and the two Irish associations could no longer ignore each other's existence. In March 1950 the IFA fielded four players born in the Free State in a World Cup qualifier against Wales. The players had previously represented the FAI side in the same competition. FIFA intervened to restrict players' eligibility based on the political border and in 1953 they ruled that the IFA team would in future compete as Northern Ireland while the FAI would play as the Republic of Ireland. Because the British Championship was not regulated by FIFA, however, the IFA team continued to play as Ireland in the annual domestic tournament.
Ireland resumed international football on 28 September 1946 when England visited Belfast and hammered the home team 7-2. As members of FIFA, the team entered the 1950 World Cup but failed to qualify (the 1949-1950 British Championship served as the qualifying competition).
A change kit was not required during this period.
Northern Ireland 1952-1957
Following FIFA's intervention, the IFA's team played as Northern Ireland from 1953, having reverted to their old crest the previous season. Their performances did not improve overall, however, and they finished in third or fourth place in the Home Championship apart from the 1956 tournament, which was tied four ways. In 1954 the old baggy shirts and shorts were replaced with the new "continental" style strip.
Northern Ireland 1957-1960
In late 1957 the old blue stockings were changed to green and white ones and the crest was redesigned. Wearing this kit, Northern Ireland qualified for the 1958 World Cup finals in Sweden, having eliminated Italy. They went on to enjoy their best ever performance, reaching the quarter-finals where they were eliminated by France. In 1958 and 1959, the Irish tied with England for the British Championship.
Once again, a change kit was not needed in this period.