Blockhouse

An edifice or structure of heavy timbers or logs for military defense, having its sides loopholed for musketry, and often an upper story projecting over the lower, or so placed upon it as to have its sides make an angle wit the sides of the lower story, thus enabling the defenders to fire downward, and in all directions; -- formerly much used in America and Germany.

A house of squared logs.

a stronghold that is reinforced for protection from enemy fire; with apertures for defensive fire