Countries will go to war if and when they believe they have a cause for war.
Some countries have a policy of avoiding war, and will only fight in their own defence; while others will agressively use violence on a regular basis. Usually these agressors will try to justify their agression by claiming it to be self defence. Some other countries will fight in defense of other nations if they believe the cause is just.
Most countries go to war for two reasons. The two reasons why countries go to war are because of power and money.
Kids continued to attend school during World War 1. In countries that had compulsory education before the war, nearly all kids continued to go to school. In many countries education was compulsory only up to age 14 or in some cases, only 13. In some European countries there were educational reforms in the aftermath of the war.
There is no way to answer this- wars go back to before there were reliable records.
Survival.
States do not go to war. Countries go to war because they do not agree on things.
because of economic treatys other countries were forced to after Germany used the assasination of archduke ferdinad as a reson to go to war.
When countries all over the world are in a war.
Not all countries are at war
there wasnt really a first 2 countries... it was really almost all of the countries in Europe at that time... they all had a bunch of alliances and forced each other into war... they were also building their military over the years, and they were just waiting for an excuse to let them go...
All of them hence the name WORLD WAR
many similarities it all depends in what countries if all there has been war in all countries
All countries fighting in World War 2 used weapons.