<s>
The	O
bombe	B-Device
(	O
)	O
was	O
an	O
electro-mechanical	O
device	O
used	O
by	O
British	O
cryptologists	O
to	O
help	O
decipher	O
German	O
Enigma-machine-encrypted	O
secret	O
messages	O
during	O
World	O
War	O
II	O
.	O
</s>
<s>
The	O
US	O
Navy	O
and	O
US	O
Army	O
later	O
produced	O
their	O
own	O
machines	O
to	O
the	O
same	O
functional	O
specification	O
,	O
albeit	O
engineered	O
differently	O
both	O
from	O
each	O
other	O
and	O
from	O
Polish	O
and	O
British	O
bombes	B-Device
.	O
</s>
<s>
The	O
British	O
bombe	B-Device
was	O
developed	O
from	O
a	O
device	O
known	O
as	O
the	O
"	O
bomba	B-Device
"	O
(	O
)	O
,	O
which	O
had	O
been	O
designed	O
in	O
Poland	O
at	O
the	O
Biuro	O
Szyfrów	O
(	O
Cipher	O
Bureau	O
)	O
by	O
cryptologist	O
Marian	O
Rejewski	O
,	O
who	O
had	O
been	O
breaking	O
German	O
Enigma	O
messages	O
for	O
the	O
previous	O
seven	O
years	O
,	O
using	O
it	O
and	O
earlier	O
machines	O
.	O
</s>
<s>
The	O
initial	O
design	O
of	O
the	O
British	O
bombe	B-Device
was	O
produced	O
in	O
1939	O
at	O
the	O
UK	O
Government	O
Code	O
and	O
Cypher	O
School	O
(	O
GC&CS	O
)	O
at	O
Bletchley	O
Park	O
by	O
Alan	O
Turing	O
,	O
with	O
an	O
important	O
refinement	O
devised	O
in	O
1940	O
by	O
Gordon	O
Welchman	O
.	O
</s>
<s>
The	O
first	O
bombe	B-Device
,	O
code-named	O
Victory	O
,	O
was	O
installed	O
in	O
March	O
1940	O
while	O
the	O
second	O
version	O
,	O
Agnus	O
Dei	O
or	O
Agnes	O
,	O
incorporating	O
Welchman	O
's	O
new	O
design	O
,	O
was	O
working	O
by	O
August	O
1940	O
.	O
</s>
<s>
The	O
bombe	B-Device
was	O
designed	O
to	O
discover	O
some	O
of	O
the	O
daily	O
settings	O
of	O
the	O
Enigma	O
machines	O
on	O
the	O
various	O
German	O
military	O
networks	O
:	O
specifically	O
,	O
the	O
set	O
of	O
rotors	O
in	O
use	O
and	O
their	O
positions	O
in	O
the	O
machine	O
;	O
the	O
rotor	O
core	O
start	O
positions	O
for	O
the	O
message	O
—	O
the	O
message	O
key	O
—	O
and	O
one	O
of	O
the	O
wirings	O
of	O
the	O
plugboard	O
.	O
</s>
<s>
The	O
repeated	O
changes	O
of	O
the	O
electrical	O
pathway	O
from	O
the	O
keyboard	O
to	O
the	O
lampboard	O
implement	O
a	O
polyalphabetic	B-Algorithm
substitution	I-Algorithm
cipher	I-Algorithm
,	O
which	O
turns	O
plaintext	O
into	O
ciphertext	O
and	O
back	O
again	O
.	O
</s>
<s>
If	O
all	O
message	O
traffic	O
for	O
a	O
day	O
used	O
the	O
same	O
rotor	O
starting	O
position	O
,	O
then	O
frequency	O
analysis	O
for	O
each	O
position	O
could	O
recover	O
the	O
polyalphabetic	B-Algorithm
substitutions	I-Algorithm
.	O
</s>
<s>
If	O
different	O
rotor	O
starting	O
positions	O
were	O
used	O
,	O
then	O
overlapping	O
portions	O
of	O
a	O
message	O
could	O
be	O
found	O
using	O
the	O
index	B-General_Concept
of	I-General_Concept
coincidence	I-General_Concept
.	O
</s>
<s>
This	O
regularity	O
was	O
exploited	O
by	O
Welchman	O
's	O
"	O
diagonal	O
board	O
"	O
enhancement	O
to	O
the	O
bombe	B-Device
,	O
which	O
vastly	O
increased	O
its	O
efficiency	O
.	O
</s>
<s>
In	O
1941	O
the	O
German	O
navy	O
introduced	O
a	O
version	O
of	O
Enigma	O
with	O
a	O
rotatable	O
reflector	O
(	O
the	O
M4	O
or	O
Four-rotor	O
Enigma	O
)	O
for	O
communicating	O
with	O
its	O
U-boats	B-Operating_System
.	O
</s>
<s>
By	O
late	O
1941	O
a	O
change	O
in	O
German	O
Navy	O
fortunes	O
in	O
the	O
Battle	O
of	O
the	O
Atlantic	O
,	O
combined	O
with	O
intelligence	O
reports	O
,	O
convinced	O
Admiral	O
Karl	O
Dönitz	O
that	O
the	O
Allies	O
were	O
able	O
to	O
read	O
the	O
German	O
Navy	O
's	O
coded	O
communications	O
,	O
and	O
a	O
fourth	O
rotor	O
with	O
unknown	O
wiring	O
was	O
added	O
to	O
German	O
Navy	O
Enigmas	O
used	O
for	O
U-boat	B-Operating_System
communications	O
,	O
producing	O
the	O
Triton	O
system	O
,	O
known	O
at	O
Bletchley	O
Park	O
as	O
Shark	O
.	O
</s>
<s>
In	O
February	O
1942	O
the	O
change	O
in	O
the	O
number	O
of	O
rotors	O
used	O
became	O
official	O
,	O
and	O
the	O
Allies	O
 '	O
ability	O
to	O
read	O
German	O
submarines	O
 '	O
messages	O
ceased	O
until	O
a	O
snatch	O
from	O
a	O
captured	O
U-boat	B-Operating_System
revealed	O
not	O
only	O
the	O
four-rotor	O
machine	O
's	O
ability	O
to	O
emulate	O
a	O
three-rotor	O
machine	O
,	O
but	O
also	O
that	O
the	O
fourth	O
rotor	O
did	O
not	O
move	O
during	O
a	O
message	O
.	O
</s>
<s>
The	O
first	O
half	O
of	O
1942	O
was	O
the	O
"	O
Second	O
Happy	O
Time	O
"	O
for	O
the	O
German	O
U-boats	B-Operating_System
,	O
with	O
renewed	O
success	O
in	O
attacking	O
Allied	O
shipping	O
.	O
</s>
<s>
The	O
bombe	B-Device
identified	O
possible	O
initial	O
positions	O
of	O
the	O
rotor	O
cores	O
and	O
the	O
stecker	O
partner	O
of	O
a	O
specified	O
letter	O
for	O
a	O
set	O
of	O
wheel	O
orders	O
.	O
</s>
<s>
In	O
the	O
words	O
of	O
Gordon	O
Welchman	O
,	O
"	O
...	O
the	O
task	O
of	O
the	O
bombe	B-Device
was	O
simply	O
to	O
reduce	O
the	O
assumptions	O
of	O
wheel	O
order	O
and	O
scrambler	O
positions	O
that	O
required	O
'	O
further	O
analysis	O
 '	O
to	O
a	O
manageable	O
number	O
"	O
.	O
</s>
<s>
The	O
bombe	B-Device
was	O
an	O
electro-mechanical	O
device	O
that	O
replicated	O
the	O
action	O
of	O
several	O
Enigma	O
machines	O
wired	O
together	O
.	O
</s>
<s>
The	O
standard	O
British	O
bombe	B-Device
contained	O
36	O
Enigma	O
equivalents	O
,	O
each	O
with	O
three	O
drums	O
wired	O
to	O
produce	O
the	O
same	O
scrambling	O
effect	O
as	O
the	O
Enigma	O
rotors	O
.	O
</s>
<s>
A	O
bombe	B-Device
could	O
run	O
two	O
or	O
three	O
jobs	O
simultaneously	O
.	O
</s>
<s>
If	O
the	O
menu	O
contained	O
12	O
or	O
fewer	O
letters	O
,	O
three	O
different	O
wheel	O
orders	O
could	O
be	O
run	O
on	O
one	O
bombe	B-Device
;	O
if	O
more	O
than	O
12	O
letters	O
,	O
only	O
two	O
.	O
</s>
<s>
In	O
order	O
to	O
simulate	O
Enigma	O
rotors	O
,	O
each	O
rotor	O
drum	O
of	O
the	O
bombe	B-Device
had	O
two	O
complete	O
sets	O
of	O
contacts	O
,	O
one	O
for	O
input	O
towards	O
the	O
reflector	O
and	O
the	O
other	O
for	O
output	O
from	O
the	O
reflector	O
,	O
so	O
that	O
the	O
reflected	O
signal	O
could	O
pass	O
back	O
through	O
a	O
separate	O
set	O
of	O
contacts	O
.	O
</s>
<s>
The	O
bombe	B-Device
drums	O
were	O
arranged	O
with	O
the	O
top	O
one	O
of	O
the	O
three	O
simulating	O
the	O
left-hand	O
rotor	O
of	O
the	O
Enigma	O
scrambler	O
,	O
the	O
middle	O
one	O
the	O
middle	O
rotor	O
,	O
and	O
the	O
bottom	O
one	O
the	O
right-hand	O
rotor	O
.	O
</s>
<s>
At	O
each	O
position	O
of	O
the	O
rotors	O
,	O
an	O
electric	O
current	O
would	O
or	O
would	O
not	O
flow	O
in	O
each	O
of	O
the	O
26	O
wires	O
,	O
and	O
this	O
would	O
be	O
tested	O
in	O
the	O
bombe	B-Device
's	O
comparator	O
unit	O
.	O
</s>
<s>
The	O
operator	O
would	O
record	O
the	O
candidate	O
solution	O
by	O
reading	O
the	O
positions	O
of	O
the	O
indicator	O
drums	O
and	O
the	O
indicator	O
unit	O
on	O
the	O
Bombe	B-Device
's	O
right-hand	O
end	O
panel	O
.	O
</s>
<s>
Typically	O
,	O
there	O
were	O
many	O
false	O
bombe	B-Device
stops	O
before	O
the	O
correct	O
one	O
was	O
found	O
.	O
</s>
<s>
A	O
bombe	B-Device
run	O
involved	O
a	O
cryptanalyst	O
first	O
obtaining	O
a	O
crib	O
—	O
a	O
section	O
of	O
plaintext	O
that	O
was	O
thought	O
to	O
correspond	O
to	O
the	O
ciphertext	O
.	O
</s>
<s>
Once	O
a	O
suitable	O
crib	O
had	O
been	O
decided	O
upon	O
,	O
the	O
cryptanalyst	O
would	O
produce	O
a	O
menu	O
for	O
wiring	O
up	O
the	O
bombe	B-Device
to	O
test	O
the	O
crib	O
against	O
the	O
ciphertext	O
.	O
</s>
<s>
Building	O
up	O
these	O
relationships	O
into	O
such	O
a	O
diagram	O
provided	O
the	O
menu	O
from	O
which	O
the	O
bombe	B-Device
connections	O
and	O
drum	O
start	O
positions	O
would	O
be	O
set	O
up	O
.	O
</s>
<s>
The	O
more	O
loops	O
in	O
the	O
menu	O
,	O
the	O
more	O
candidate	O
rotor	O
settings	O
the	O
bombe	B-Device
could	O
reject	O
,	O
and	O
hence	O
the	O
fewer	O
false	O
stops	O
.	O
</s>
<s>
Alan	O
Turing	O
conducted	O
a	O
very	O
substantial	O
analysis	O
(	O
without	O
any	O
electronic	O
aids	O
)	O
to	O
estimate	O
how	O
many	O
bombe	B-Device
stops	O
would	O
be	O
expected	O
according	O
to	O
the	O
number	O
of	O
letters	O
in	O
the	O
menu	O
and	O
the	O
number	O
of	O
loops	O
.	O
</s>
<s>
Recent	O
bombe	B-Device
simulations	O
have	O
shown	O
similar	O
results	O
.	O
</s>
<s>
The	O
cryptanalyst	O
hypothesised	O
one	O
plugboard	O
interconnection	O
for	O
the	O
bombe	B-Device
to	O
test	O
.	O
</s>
<s>
To	O
automate	O
these	O
logical	O
deductions	O
,	O
the	O
bombe	B-Device
took	O
the	O
form	O
of	O
an	O
electrical	O
circuit	O
.	O
</s>
<s>
To	O
form	O
this	O
circuit	O
,	O
the	O
bombe	B-Device
used	O
several	O
sets	O
of	O
Enigma	O
rotor	O
stacks	O
wired	O
up	O
together	O
according	O
to	O
the	O
instructions	O
given	O
on	O
a	O
menu	O
,	O
derived	O
from	O
a	O
crib	O
.	O
</s>
<s>
Practical	O
bombes	B-Device
used	O
several	O
stacks	O
of	O
rotors	O
spinning	O
together	O
to	O
test	O
multiple	O
hypotheses	O
about	O
possible	O
setups	O
of	O
the	O
Enigma	O
machine	O
,	O
such	O
as	O
the	O
order	O
of	O
the	O
rotors	O
in	O
the	O
stack	O
.	O
</s>
<s>
While	O
Turing	O
's	O
bombe	B-Device
worked	O
in	O
theory	O
,	O
it	O
required	O
impractically	O
long	O
cribs	O
to	O
rule	O
out	O
sufficiently	O
large	O
numbers	O
of	O
settings	O
.	O
</s>
<s>
Gordon	O
Welchman	O
came	O
up	O
with	O
a	O
way	O
of	O
using	O
the	O
symmetry	O
of	O
the	O
Enigma	O
stecker	O
to	O
increase	O
the	O
power	O
of	O
the	O
bombe	B-Device
.	O
</s>
<s>
His	O
suggestion	O
was	O
an	O
attachment	O
called	O
the	O
diagonal	O
board	O
that	O
further	O
improved	O
the	O
bombe	B-Device
's	O
effectiveness	O
.	O
</s>
<s>
The	O
Polish	O
cryptologic	O
bomba	B-Device
(	O
Polish	O
:	O
bomba	B-Device
kryptologiczna	O
;	O
plural	O
bomby	O
)	O
had	O
been	O
useful	O
only	O
as	O
long	O
as	O
three	O
conditions	O
were	O
met	O
.	O
</s>
<s>
Alan	O
Turing	O
designed	O
the	O
British	O
bombe	B-Device
on	O
a	O
more	O
general	O
principle	O
,	O
the	O
assumption	O
of	O
the	O
presence	O
of	O
text	O
,	O
called	O
a	O
crib	O
,	O
that	O
cryptanalysts	O
could	O
predict	O
was	O
likely	O
to	O
be	O
present	O
at	O
a	O
defined	O
point	O
in	O
the	O
message	O
.	O
</s>
<s>
A	O
£	O
100,000	O
budget	O
for	O
the	O
construction	O
of	O
Turing	O
's	O
machine	O
was	O
acquired	O
and	O
the	O
contract	O
to	O
build	O
the	O
bombes	B-Device
was	O
awarded	O
to	O
the	O
British	O
Tabulating	O
Machine	O
Company	O
(	O
BTM	O
)	O
at	O
Letchworth	O
.	O
</s>
<s>
On	O
the	O
front	O
of	O
each	O
bombe	B-Device
were	O
108	O
places	O
where	O
drums	O
could	O
be	O
mounted	O
.	O
</s>
<s>
The	O
bombe	B-Device
drums	O
 '	O
input	O
and	O
output	O
contacts	O
went	O
to	O
cable	O
connectors	O
,	O
allowing	O
the	O
bombe	B-Device
to	O
be	O
wired	O
up	O
according	O
to	O
the	O
menu	O
.	O
</s>
<s>
The	O
first	O
bombe	B-Device
was	O
named	O
"	O
Victory	O
"	O
.	O
</s>
<s>
Bletchley	O
retrospectively	O
attacked	O
some	O
messages	O
sent	O
during	O
this	O
period	O
using	O
the	O
captured	O
material	O
and	O
an	O
ingenious	O
Bombe	B-Device
menu	O
where	O
the	O
Enigma	O
fast	O
rotors	O
were	O
all	O
in	O
the	O
same	O
position	O
.	O
</s>
<s>
The	O
second	O
bombe	B-Device
,	O
named	O
"	O
Agnus	O
dei	O
"	O
,	O
later	O
shortened	O
to	O
"	O
Agnes	O
"	O
,	O
or	O
"	O
Aggie	O
"	O
,	O
was	O
equipped	O
with	O
Welchman	O
's	O
diagonal	O
board	O
,	O
and	O
was	O
installed	O
on	O
8	O
August	O
1940	O
;	O
"	O
Victory	O
"	O
was	O
later	O
returned	O
to	O
Letchworth	O
to	O
have	O
a	O
diagonal	O
board	O
fitted	O
.	O
</s>
<s>
The	O
bombes	B-Device
were	O
later	O
moved	O
from	O
"	O
Hut	O
1	O
"	O
to	O
"	O
Hut	O
11	O
"	O
.	O
</s>
<s>
The	O
bombe	B-Device
was	O
referred	O
to	O
by	O
Group	O
Captain	O
Winterbotham	O
as	O
a	O
"	O
Bronze	O
Goddess	O
"	O
because	O
of	O
its	O
colour	O
.	O
</s>
<s>
Because	O
of	O
the	O
danger	O
of	O
bombes	B-Device
at	O
Bletchley	O
Park	O
being	O
lost	O
if	O
there	O
were	O
to	O
be	O
a	O
bombing	O
raid	O
,	O
bombe	B-Device
outstations	O
were	O
established	O
,	O
at	O
Adstock	O
,	O
Gayhurst	O
and	O
Wavendon	O
,	O
all	O
in	O
Buckinghamshire	O
.	O
</s>
<s>
In	O
June	O
–	O
August	O
1941	O
there	O
were	O
4	O
to	O
6	O
bombes	B-Device
at	O
Bletchley	O
Park	O
,	O
and	O
when	O
Wavendon	O
was	O
completed	O
,	O
Bletchley	O
,	O
Adstock	O
and	O
Wavenden	O
had	O
a	O
total	O
of	O
24	O
to	O
30	O
bombes	B-Device
.	O
</s>
<s>
When	O
Gayhurst	O
became	O
operational	O
there	O
were	O
a	O
total	O
of	O
40	O
to	O
46	O
bombes	B-Device
,	O
and	O
it	O
was	O
expected	O
that	O
the	O
total	O
would	O
increase	O
to	O
about	O
70	O
bombes	B-Device
run	O
by	O
some	O
700	O
Wrens	O
(	O
Women	O
's	O
Royal	O
Naval	O
Service	O
)	O
.	O
</s>
<s>
But	O
in	O
1942	O
with	O
the	O
introduction	O
of	O
the	O
naval	O
four-rotor	O
Enigma	O
,	O
"	O
far	O
more	O
than	O
seventy	O
bombes	B-Device
"	O
would	O
be	O
needed	O
.	O
</s>
<s>
New	O
outstations	O
were	O
established	O
at	O
Stanmore	O
and	O
Eastcote	O
,	O
and	O
the	O
Wavendon	O
and	O
Adstock	O
bombes	B-Device
were	O
moved	O
to	O
them	O
,	O
though	O
the	O
Gayhurst	O
site	O
was	O
retained	O
.	O
</s>
<s>
The	O
few	O
bombes	B-Device
left	O
at	O
Bletchley	O
Park	O
were	O
used	O
for	O
demonstration	O
and	O
training	O
purposes	O
only	O
.	O
</s>
<s>
Production	O
of	O
bombes	B-Device
by	O
BTM	O
at	O
Letchworth	O
in	O
wartime	O
conditions	O
was	O
nowhere	O
near	O
as	O
rapid	O
as	O
the	O
Americans	O
later	O
achieved	O
at	O
NCR	O
in	O
Dayton	O
,	O
Ohio	O
.	O
</s>
<s>
Sergeant	O
Jones	O
was	O
given	O
the	O
overall	O
responsibility	O
for	O
Bombe	B-Device
maintenance	O
by	O
Edward	O
Travis	O
.	O
</s>
<s>
Later	O
Squadron	O
Leader	O
and	O
not	O
to	O
be	O
confused	O
with	O
Eric	O
Jones	O
,	O
he	O
was	O
one	O
of	O
the	O
original	O
bombe	B-Device
maintenance	O
engineers	O
,	O
and	O
experienced	O
in	O
BTM	O
techniques	O
.	O
</s>
<s>
There	O
were	O
104	O
brushes	O
per	O
drum	O
,	O
720	O
drums	O
per	O
bombe	B-Device
,	O
and	O
ultimately	O
around	O
200	O
bombes	B-Device
.	O
</s>
<s>
After	O
World	O
War	O
II	O
,	O
some	O
fifty	O
bombes	B-Device
were	O
retained	O
at	O
RAF	O
Eastcote	O
,	O
while	O
the	O
rest	O
were	O
destroyed	O
.	O
</s>
<s>
The	O
surviving	O
bombes	B-Device
were	O
put	O
to	O
work	O
,	O
possibly	O
on	O
Eastern	O
bloc	O
ciphers	O
.	O
</s>
<s>
Smith	O
cites	O
the	O
official	O
history	O
of	O
the	O
bombe	B-Device
as	O
saying	O
that	O
"	O
some	O
of	O
these	O
machines	O
were	O
to	O
be	O
stored	O
away	O
but	O
others	O
were	O
required	O
to	O
run	O
new	O
jobs	O
and	O
sixteen	O
machines	O
were	O
kept	O
comparatively	O
busy	O
on	O
menus.	O
"	O
</s>
<s>
A	O
program	O
was	O
initiated	O
by	O
Bletchley	O
Park	O
to	O
design	O
much	O
faster	O
bombes	B-Device
that	O
could	O
decrypt	O
the	O
four-rotor	O
system	O
in	O
a	O
reasonable	O
time	O
.	O
</s>
<s>
Despite	O
some	O
worthwhile	O
collaboration	O
amongst	O
the	O
cryptanalysts	O
,	O
their	O
superiors	O
took	O
some	O
time	O
to	O
achieve	O
a	O
trusting	O
relationship	O
in	O
which	O
both	O
British	O
and	O
American	O
bombes	B-Device
were	O
used	O
to	O
mutual	O
benefit	O
.	O
</s>
<s>
The	O
four	O
returned	O
to	O
America	O
after	O
ten	O
weeks	O
,	O
with	O
a	O
naval	O
radio	B-Device
direction	I-Device
finding	I-Device
unit	O
and	O
many	O
documents	O
including	O
a	O
'	O
paper	O
Enigma	O
 '	O
.	O
</s>
<s>
The	O
main	O
response	O
to	O
the	O
Four-rotor	O
Enigma	O
was	O
the	O
US	O
Navy	O
bombe	B-Device
,	O
which	O
was	O
manufactured	O
in	O
much	O
less	O
constrained	O
facilities	O
than	O
were	O
available	O
in	O
wartime	O
Britain	O
.	O
</s>
<s>
Colonel	O
John	O
Tiltman	O
,	O
who	O
later	O
became	O
Deputy	O
Director	O
at	O
Bletchley	O
Park	O
,	O
visited	O
the	O
US	O
Navy	O
cryptanalysis	O
office	O
(	O
OP-20-G	O
)	O
in	O
April	O
1942	O
and	O
recognised	O
America	O
's	O
vital	O
interest	O
in	O
deciphering	O
U-boat	B-Operating_System
traffic	O
.	O
</s>
<s>
The	O
urgent	O
need	O
,	O
doubts	O
about	O
the	O
British	O
engineering	O
workload	O
and	O
slow	O
progress	O
,	O
prompted	O
the	O
US	O
to	O
start	O
investigating	O
designs	O
for	O
a	O
Navy	O
bombe	B-Device
,	O
based	O
on	O
the	O
full	O
blueprints	B-Application
and	O
wiring	O
diagrams	O
received	O
by	O
US	O
Naval	O
Lieutenants	O
Robert	O
Ely	O
and	O
Joseph	O
Eachus	O
at	O
Bletchley	O
Park	O
in	O
July	O
1942	O
.	O
</s>
<s>
An	O
all	O
electronic	O
solution	O
to	O
the	O
problem	O
of	O
a	O
fast	O
bombe	B-Device
was	O
considered	O
,	O
but	O
rejected	O
for	O
pragmatic	O
reasons	O
,	O
and	O
a	O
contract	O
was	O
let	O
with	O
the	O
National	O
Cash	O
Register	O
Corporation	O
(	O
NCR	O
)	O
in	O
Dayton	O
,	O
Ohio	O
.	O
</s>
<s>
Alan	O
Turing	O
,	O
who	O
had	O
written	O
a	O
memorandum	O
to	O
OP-20-G	O
(	O
probably	O
in	O
1941	O
)	O
,	O
was	O
seconded	O
to	O
the	O
British	O
Joint	O
Staff	O
Mission	O
in	O
Washington	O
in	O
December	O
1942	O
,	O
because	O
of	O
his	O
exceptionally	O
wide	O
knowledge	O
about	O
the	O
bombes	B-Device
and	O
the	O
methods	O
of	O
their	O
use	O
.	O
</s>
<s>
He	O
was	O
asked	O
to	O
look	O
at	O
the	O
bombes	B-Device
that	O
were	O
being	O
built	O
by	O
NCR	O
and	O
at	O
the	O
security	O
of	O
certain	O
speech	O
cipher	O
equipment	O
under	O
development	O
at	O
Bell	O
Labs	O
.	O
</s>
<s>
He	O
was	O
able	O
to	O
show	O
that	O
it	O
was	O
not	O
necessary	O
to	O
build	O
336	O
Bombes	B-Device
,	O
one	O
for	O
each	O
possible	O
rotor	O
order	O
,	O
by	O
utilising	O
techniques	O
such	O
as	O
Banburismus	O
.	O
</s>
<s>
The	O
US	O
Navy	O
bombes	B-Device
used	O
drums	O
for	O
the	O
Enigma	O
rotors	O
in	O
much	O
the	O
same	O
way	O
as	O
the	O
British	O
bombes	B-Device
.	O
</s>
<s>
The	O
fast	O
drum	O
rotated	O
at	O
1,725	O
rpm	O
,	O
34	O
times	O
the	O
speed	O
of	O
the	O
early	O
British	O
bombes	B-Device
.	O
</s>
<s>
These	O
bombes	B-Device
were	O
faster	O
,	O
and	O
soon	O
more	O
available	O
,	O
than	O
the	O
British	O
bombes	B-Device
at	O
Bletchley	O
Park	O
and	O
its	O
outstations	O
.	O
</s>
<s>
Production	O
was	O
stopped	O
in	O
September	O
1944	O
after	O
121	O
bombes	B-Device
had	O
been	O
made	O
.	O
</s>
<s>
The	O
last-manufactured	O
US	O
Navy	O
bombe	B-Device
is	O
on	O
display	O
at	O
the	O
US	O
National	O
Cryptologic	O
Museum	O
.	O
</s>
<s>
Jack	O
Ingram	O
,	O
former	O
Curator	O
of	O
the	O
museum	O
,	O
describes	O
being	O
told	O
of	O
the	O
existence	O
of	O
a	O
second	O
bombe	B-Device
and	O
searching	O
for	O
it	O
but	O
not	O
finding	O
it	O
whole	O
.	O
</s>
<s>
The	O
US	O
Army	O
Bombe	B-Device
was	O
physically	O
very	O
different	O
from	O
the	O
British	O
and	O
US	O
Navy	O
bombes	B-Device
.	O
</s>
<s>
It	O
could	O
,	O
however	O
,	O
handle	O
one	O
problem	O
that	O
the	O
bombes	B-Device
with	O
drums	O
could	O
not	O
.	O
</s>
<s>
The	O
set	O
of	O
ten	O
bombes	B-Device
consisted	O
of	O
a	O
total	O
of	O
144	O
Enigma-equivalents	O
,	O
each	O
mounted	O
on	O
a	O
rack	O
approximately	O
long	O
high	O
and	O
wide	O
.	O
</s>
<s>
In	O
1994	O
a	O
group	O
led	O
by	O
John	O
Harper	O
of	O
the	O
BCS	O
Computer	O
Conservation	O
Society	O
started	O
a	O
project	O
to	O
build	O
a	O
working	O
replica	O
of	O
a	O
bombe	B-Device
.	O
</s>
<s>
The	O
Bombe	B-Device
rebuild	O
was	O
relocated	O
to	O
The	O
National	O
Museum	O
of	O
Computing	O
on	O
Bletchley	O
Park	O
in	O
May	O
2018	O
,	O
the	O
new	O
gallery	O
officially	O
re-opening	O
on	O
23	O
June	O
2018	O
.	O
</s>
