Combination reaction when nitrogen combines with hydrogen, ammonia is formed?

##N_2 + 3H_2 -> 2NH_3##

This is an example of a combination reaction. It can also be called a synthesis reaction. The reaction has huge historical importance.

The reaction is carried out for industrial practice using the Haber-Bosch process which was developed by Fritz Haber in Germany in the early 1900's. The Haber process was used by Germany to increase their production of ammonia (used for fertilizer) which allowed the country to increase food production without being dependent on importing fertilizer. This is one factor which allowed Germany to enter into WWI.

Haber was Jewish and had to leave Germany when the Nazis came to power. He was viewed negatively by many scientists because he did work during WWI to develop chemical weapons for Germany.