Instruction on the Fortification of Cities

of the bastion original: "pastey"; Dürer’s term for a massive, semi-circular or D-shaped stone fortification designed to house heavy guns., to defend against flanking fire original: "streych"; refers to the ability to fire along the face of a wall to clear away attackers. all around, from one side of the city wall to the
other. This is done so that if someone fell into the ditch, they would not
so easily reach the embrasures original: "schießlöchern"; the openings in the fortification through which cannons or firearms are discharged.. However, the
bastion should project a considerable distance out from the city walls into the city ditch, as
follows hereafter. Also, the bastion is positioned in such a way that one may defend
as well to both sides as to the front; if it can also be made to defend toward the rear,
it is even better. I am speaking here of dry city ditches; however, where one can have
water-filled ditches, it is more advantageous.

Initially, a ground plan is drafted on a flat surface with two lines, .a.c., representing the
shape of the corner of the city walls where one intends to build the bastion. And where
the two lines .a.c. close a corner, place a .b. there. Afterward, cut off the corner .b.
with a straight line that is three hundred feet original: "schůch"; a historical unit of measurement roughly equivalent to a modern foot. long, and mark
its two ends with .d. and .e., so that .d.b. and .b.e. remain of
equal length, just as it is drafted hereafter. However, when I later proceed to the construction,
I will demonstrate such a concept with a larger figure than these two following ones.

A geometric diagram representing the layout of a fortification. Two angled lines (representing a city wall corner) are labeled at their outer ends with 'a' and 'c'. A horizontal line segment intersects these two lines and is labeled 'd' at its left end and 'e' at its right end. The intersection point of the two original angled lines is referred to as 'b' in the text below.

Afterward, a cross-line .f.g. is drafted through the middle of the line .d.e. and the corner .b., so that
.d.e. and .f.g. form four equal angles, and that .g. stands toward the ditch. And the center
point that makes the four angles shall be .h. Then, one places a point .i. on the line .g.h.,
90 feet out from the .h. toward the .g. Afterward, a compass original: "zirckel" is placed with
one foot on the line .f.h. at a point .k. (which must be found), and with the other
foot, one draws a circular line original: "zirckellini"; an arc or curved path. .d.i.e. This circular line is the plan for the outward curve
in the ditch at the bastions. Now, the rear foundation within the city should also be calculated
as deep as the front, even though one perhaps does not need it as deep as the foundation in the
ditch before the line .d.e. This is so that if this bastion must be the same in the back and front,
one could better arrange it with ditches and whatever is necessary for it. Therefore, one proceeds
with a square original: "fierung"; a rectangular or squared layout. from the line .d.e. straight backward sixty feet deep,
at the two corner sides .l.m. Thus, the bastion is entirely enclosed at the base with these lines.
If one wished for a bastion to stand freely, one could make it the same in the back as in the front,
provided that a sturdy walkway—which could not be broken down—was allowed to reach it from
the side or wherever it was most convenient. But before I write further, I will draft this
plan with the squared part toward the city through lines as described above.