were many factors to be considered and many alternatives
to be decided upon in planning and carrying out a B-26
mission against a rail or road bridge.
came the question of which bridge to hit to most effectively
cut the Germans off from their Supplies. The answer
came from analysis of intelligence information and aerial
a particular bridge was singled out for attack because
of the bottleneck blasting it would create, operational
policy was to keep on hitting it with as many consecutive
missions as necessary to knock it out before going on
to the next one. That way the Germans didn't have time
to concentrate their flak.
course one bridge being cut did not deter the enemy
for long. The Germans simply took their trains to the
edge of a bombed viaduct, unloaded their supplies into
trucks and hauled them around to the other side to be
loaded on another train going south. So, in order to
maintain a complete break in a rail line many cuts within
a short distance had to be made to prevent this train-truck
enemy countered by dispersing bridge repair battalions
and spare steel spans along the rail lines so that within
a few hours after the bombardment replacement could
be underway. Our answer was to step up the frequency
of B-26 attacks.
best approach to the target had to be decided on, and
this was difficult at times. Some bridges were so small
or so well hidden in mountain folds that picking them
up at all became a real problem. The approach also had
to take known flak positions into account.
of attack was another consideration. Most bridges were
attacked at a ninety degree angle, from altitudes of
9,000 to 12,000 feet. This allowed the bombardier to
make deflection errors half the length of the bridge
and it gave him an excellent horizontal line to put
the cross hair of his bomb sight on. In most cases the
drop pattern was set to have bombs first strike just
short of the bridge and then extend across it. Larger
bridges were usually hit at about forty-five degrees,
depending on the range or string spread of the bombs.
weather report had to be carefully and accurately analyzed.
had to be considered. An upwind approach, for instance,
improves accuracy by decreasing the formation's ground
speed so that a standard length bomb run can start at
a point closer to the target.
was another factor. Marauder bridge-busting was best
done by flights rather than by "boxes
critical decision had to be made on the intervalometer
(bomb fall) setting. To hit a thirty-foot wide bridge,
bombs of the lead ship of each flight which carried
the Norden bombsight might be set to fall at, say, sixty-foot
intervals. Wing ship bomb intervals might be set at
thirty feet. The lead ship's string would be set to
start short of the target to compensate for the dropping
lag between lead and wing ships. The sixty-foot interval
would bring the last few bombs of the lead ship across
the bridge. Wing ship strings would then be directly
across the bridge, their thirty-foot setting preventing
and types of bomb to be used and fuse settings also
had to be deter-mined. Bombs on bridge busting
missions were generally one or two thousand pound demolition
types fitted with either delay or instantaneous fuses,
sometimes with an armor-piercing case.
was important to use the smallest bomb possible so more
bombs per airplane could be carried. A 1,000-pounder
would cut a bridge not more than twenty-five feet wide
- if the bomb was properly fused. If a bridge was more
than twenty-five feet wide, a 2,000-pound bomb had to
be used, but this cut the probability of one airplane
obtaining a hit at least in half.
fuses (usually .01 seconds) permitted the bombs to penetrate
deep into the bridge before exploding. Instantaneous
fuses, of course, blew up the bombs on contact and were
generally used on steel suspension bridges to prevent
the bomb from crashing through the structural girders
and exploding in the open air beneath.
a particularly tough and rugged bridge, such as one
with a heavy reinforced concrete floor or one of granite,
bombs with an armor-piercing shell were used. This gave
the bomb a chance to penetrate without rupturing and
then explode. The delay was usually .025 seconds, enough
to permit penetration into the concrete so that the
explosion would push outward, crumbing the bridge.
selected B-26s scattered through the formation would
drop a few long-delay bombs in an effort to hinder later
bridge repairs. These bombs would burrow into the earth
a number of feet and then curve out laterally. They
couldn't be excavated before they might go off and the
enemy couldn't tell exactly where they were unless he
did plenty of digging. They might explode as long as
twenty-four hours after dropping and this posed both
a psychological and a real hazard to repair workers.