Why might the war cause an economic recession or depression in europe

The war might cause an economic recession or depression in Europe because wars are very expensive. Taxes are usually doubled in order to pay for supplies and the production of new machinery needed for the war.

Ok so usually war is a good profitable thing for a country but in some cases the country will produce more war materials than the economic system can handle and it will cause it to fall through and leave the country broke because they have war materials but not the money to produce it