If you're talking about WW2, it's the battle of Stalingrad.
If it's about WW1, it would probably be Verdun.
Turkey has a largely homogeneous population in that the majority of the population is Sunni Muslim of Turkish origin. However, there are other ethnic and religious groups within Turkey such as the Kurds and also Shi'a Muslims. The greatest challenge to Turkey due to its internal diversity is the threat of secession and also issues related to national security posed by the Kurdish population. Another major issue today in Turkey is the presence of Syrian refugees and also fighters involved in the Syrian conflict which pose national security threats as well.
I’m not sure if you mean technological and economic development or just products coming out kind of development.
Well I’m not gonna write out two paragraphs but some important tech and economical developments were:
The radio became widespread. It was welcomed by the public and by 1934 almost 60% of the US had radio access. Sports events, news, dramas and more were broadcasted through the radio.
Stock markets across the west developed negatively. On Black Tuesday, stock markets crashed, sending the world into the Great Depression.