58. " " TAKING OF AN ARTILLERY TOWER (_to face_) 266 59. THE BASTIONS OF ERRARD DE LE BAR-LE-DUC 277 60. THE NORTH WORK 279 61. ONE OF THE BASTIONS 280 62. SIXTH SIEGE.--GALAS' WORKS OF APPROACH 289 63. " " THE ATTACK ON ONE OF THE BESIEGERS' PLACE D'ARMES (_to face_) 290 64. " " FORCIA'S PLAN OF SIEGE 298 65. VAUBAN'S DEFENCES 305 66. VAUBAN'S OUTWORK 307 67. SECTIONS OF THE OUTWORK 309 68. TRACE OF THE OUTWORK 311 69. REVÊTEMENT OF THE BASTIONS 313 70. SEVENTH SIEGE.--THE THEORETICAL ATTACK OF VAUBAN'S WORK (_to face_) 337 71. " " THE THIRD PARALLEL AND THE CROWNING OF THE COUVERT WAY (_to face_) 338 72. " " CAPTAIN ALLAUD'S ADVANCED WORK 341 73. " " SECTIONS AND INTERIOR VIEW OF THE WORK 347 74. " " CAPTAIN ALLAUD'S CRÉMAILLÈRE WORK 341 75. " " ATTACK ON THE WORKS OF COUNTER-APPROACH 347 76. ILLUSTRATIONS OF THE PRINCIPLES OF ATTACK AND DEFENCE 358 77. DITTO 358 78. DITTO 359 79. APPLICATION OF THE PRINCIPLE: "WHAT DEFENDS SHOULD ITSELF BE DEFENDED" 361 80. ILLUSTRATION OF THE ALTERED CONDITIONS NECESSITATED BY ARTILLERY OF LONG RANGE 362 81. PLAN OF FORTRESS SHOWING HOW THOSE CONDITIONS ARE MET 364 82. BLOCK PLAN OF THE DETACHED FORTS 365 83. THEORETICAL PLAN OF A MODERN FORTRESS 366 84. EMPLOYMENT OF THE POLYGONAL SYSTEM, DETACHED FORTS 372 85. DEFENSIVE SYSTEM OF GREAT INTRENCHED CAMP 375 ANNALS OF A FORTRESS. "Je sçais bien qu'il faut perdre, qu'il faut gaigner, et n'y a rien d'imprenable; mais desirez cent mil fois plustost la mort si tous moyens ne vous deffaillent, que dire ce méchant et vilain mot: 'JE LA RENDS.'"--_Comment._ de MONTLUC. CHAPTER I. _THE FIRST RETREAT._ Many winters, as we are told by the old men of the district, have passed since human beings first settled in the land of Ohet, a somewhat extensive valley of varying breadth, traversed by a winding stream running southward till it flows into a great river.