Throughout the 20th century air defence was one of the fastest-evolving areas of military technology, responding to the evolution of aircraft and exploiting various enabling technologies, particularly radar, guided missiles and computing (initially electromechanical analog computing from the 1930s on, as with equipment described below). Air defence evolution covered the areas of sensors and technical fire control, weapons, and command and control. At the start of the 20th century these were either very primitive or non-existent.
What was one of the quickest areas to evolve in military technology in the 20th century?
air defence

Migration in birds is highly labile and is believed to have developed independently in many avian lineages. While it is agreed that the behavioral and physiological adaptations necessary for migration are under genetic control, some authors have argued that no genetic change is necessary for migratory behavior to develop in a sedentary species because the genetic framework for migratory behavior exists in nearly all avian lineages. This explains the rapid appearance of migratory behavior after the most recent glacial maximum.
What exists in nearly all avian lineages?
genetic framework for migratory behavior

The Tito-Stalin split had large ramifications for countries outside the USSR and Yugoslavia. It has, for example, been given as one of the reasons for the Slansky trial in Czechoslovakia, in which 14 high-level Communist officials were purged, with 11 of them being executed. Stalin put pressure on Czechoslovakia to conduct purges in order to discourage the spread of the idea of a "national path to socialism," which Tito espoused.
What country had pressure put on it by Stalin to conduct purges?
Czechoslovakia