What does it mean by kennedy "improvised remarks "?

Explanation:

Improvise is like to give a speech without practicing your own speech, and remarks mean to mention or regard with attention. So as a example of  " Kennedy's improvised remarks" is when he made a statement of MLK's assassination at Indianapolis, Indiana, April 4, 1968  

the berlin blockade was an international crisis that arose from an attempt by the soviet union, in 1948–49, to force the western allied powers (the united states, the united kingdom, and france) to abandon their post-world war ii jurisdictions in west berlin. in march 1948 the allied powers decided to unite their different occupation zones of germany into a single economic unit. in protest, the soviet representative withdrew from the allied control council. coincident with the introduction of a new deutsche mark in west berlin (as throughout west germany), which the soviets regarded as a violation of agreements with the allies, the soviet occupation forces in eastern germany began a blockade of all rail, road, and water communications between berlin and the west. on june 24 the soviets announced that the four-power administration of berlin had ceased and that the allies no longer had any rights there.