Answer:
In the short run, there is a negative correlation between the changes in wages (normally growth rate) and the rate of unemployment. Changes in wages imply changes of inflation. This relationship is known as Phillips' Curve, in honour of William Phillips, who discovered it in 1958.
Thus, the bigger the rate of inflation, the lower the unemployment. This appealing consequence made politicians think that they could get the level of employment they want just by creating more inflation.
Eventually this was not true, and studies after these years showed that this correlation fell apart, and there were combinations of high unemployment and inflation.
Why was that? The answer is expectations. If individuals know that governments (or central banks) will follow a weak monetary policy (increasing the circulation of money in the economy and therefore generating inflation) they will expect the rate of inflation to be high. Trade unions will endeavour to get rises in wages, and this will impede companies to hire more workers. Thus if the monetary authority increase inflation now, it would not get reduction of unemployment.