If there happens a World War 3, which cannot happen soon as we all know there are many organizations which are working day-night to avoid such situations but anything can happen. So, if World war or any other war happens then it may affect cryptocurrency also as trade stops and it affects economic conditions of the country. Moreover, big investors need to invest money at a greater cause then Bitcoin. So, wars will highly affect cryptocurrency.
If war starts then everything from trade to daily routine exchange get paused. The people pay more attention to peace than to trade, so not only crypto but regular currencies also falls . They try to stop the blood of innocent to be shed , they try to arrange talks for bringing peace. In order to raise the economy chart or currency worth, peace should be made obligatory