First, that few districts contain two such positions as those of the Confederates at Fredericksburg; and, secondly, that the strength of a position is measured not by the impregnability of the front, but by the security of the flanks.
"Stonewall Jackson And The American Civil War"
G. F. R. Henderson
Filibusters saw the value of a base so close to Spanish holdings, realized the impregnability of the harbor and flocked thither.
"Plotting in Pirate Seas"
Francis Rolt-Wheeler
Whether an invasion of Sikkim was either advisable or called for, was a matter in which I had no concern: nor do I offer an opinion as to the impregnability of the country if it were defended by natives otherwise a match for a British force, and having the advantage of position.
"Himalayan Journals V2."
J. D. Hooker