How hypertension causes stroke?

Hypertension or the high blood pressure causes strokes in many ways. Firstly, high blood pressure damages the inner lining of the blood vessels. When the blood vessels get damaged, the layer of fat or lipids gets deposited on the walls of the blood vessels leading to the development of atherosclerotic lesions which in turn leads to the formation of plaques resulting in the thickening of the inner walls of the arteries and decreases the flow of the blood thereby reduces the supply of oxygen to the brain tissues which in turn causes strokes.  
Secondly, if the thickened arteries rupture, the blood clots forms and these blood clots may block the blood vessels that supplies blood to the brain and thus causing the strokes. 
Thirdly, high blood pressure not only thickening the blood vessels but also narrows down the blood vessel and in the process the blood vessels becomes very weak and ruptures to cause stroke, in which bleeding occurs inside the brain and results in brain damage. The stroke can even occur if the increase in blood pressure is sharp and sudden. 
As such there are no warning symptoms for the emergence of high blood pressure, doing regular exercises and the controlled diet are the ways that help an individual to safeguard from hypertension and its consequences.