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MAP OF THE PEARL HARBOR
ATTACK
Click to enlarge
Timeline of the Pearl Harbor Attack 1941
Dates
and times of events are local time,
Hawaiian Standard Time (HST).
::: Introduction :::
Japan’s initial attack wave on December 7, 1941, was a meticulously coordinated operation and the opening move of what
Admiral Yamamoto’s Combined Fleet planners internally referred to as Operation Z (ゼット作戦, Zetto Sakusen),
the codename for the surprise attack on Pearl Harbor.
Led by Commander Mitsuo Fuchida, the first wave consisted of 183
aircraft—including torpedo bombers, dive bombers, horizontal bombers, and fighter planes—launched from
six aircraft carriers: Akagi, Kaga, Sōryū, Hiryū, Shōkaku, and Zuikaku, positioned
northwest of Oahu.
The primary objectives of this initial wave were:
- U.S. battleships and other major warships at Pearl Harbor, especially those moored along "Battleship Row"
- U.S. Army and Navy airfields around Oahu, including Hickam Field, Wheeler Field, Ford Island, Barber’s Point, and Naval Air Station Kaneohe
- Aircraft on the ground, to neutralize the potential for an aerial counterattack
This first wave was followed approximately 90 minutes later by a second wave of 170 aircraft, which inflicted further damage
on American facilities and ships. While both waves were devastating, the initial strike proved the most destructive,
critically crippling U.S. naval and air capabilities at Pearl Harbor.
Though often mistakenly grouped together, the assault on Pearl Harbor was not part of the Southern
Operation (南方作戦, Nanpō Sakusen); rather, it was a distinct naval operation—formally known as Operation AI, and
internally as Operation Z—executed by the Combined Fleet. The Southern Operation was a separate, army-led
campaign targeting Southeast Asia, including British Malaya, the Dutch East Indies, and the Philippines,
launched in parallel over December 7–8, 1941 (depending on time zone). Within hours of the Pearl Harbor strike,
Japanese forces attacked Allied positions in Hong Kong, the Philippines, Guam, Wake Island, Malaya, and
Thailand. These operations involved hundreds of aircraft and over 60,000 ground troops in Malaya alone.
The strategic goal behind this multi-theater offensive was to achieve overwhelming superiority through synchronized
surprise attacks—crippling Allied naval and air forces at the outset and securing vital resources such as oil, rubber,
and tin from Southeast Asia. In this context, Pearl Harbor served as the keystone of Japan’s broader bid to win a short,
decisive war before the Allies could fully mobilize their industrial and military power.
For more on the Japanese operation codenames, see end of this page.
Here now the timeline:
::: Timeline :::
December 6, 1941 (Saturday) — Late Afternoon
U.S. naval and diplomatic code-breakers intercept Japan’s final set of break-off communications (“14-part message”),
signaling negotiations have failed. Washington recognizes that war is imminent but learns no target details. Admiral Stark (CNO)
decides not to wake Admiral Kimmel overnight with this intelligence. Secretary of War Marshall later approves a general “combat alert”
for Pacific commands, but U.S. Army communications lines to Hawaii fail, so the warning must be sent by Western Union. The delayed
warning was transmitted via Western Union and arrived too late.
December 7, 1941 (Sunday)
3:42 AM:
USS Condor reports sighting a submarine periscope near Pearl Harbor's entrance. The contact is treated as unconfirmed and
does not prompt a full alert.
6:00 AM:
From ~230 miles north of Oahu, the Japanese carrier strike group launches the first wave of ~200 aircraft.
6:37 AM:
USS Ward spots a midget submarine and at 6:45 AM sinks it with gunfire and depth charges. This is the first U.S. combat action
of WWII. The warning sent by Ward is not escalated promptly.
7:00 AM:
The attack on Malaya (British) began when Japanese forces commenced an amphibious landing at Kota Bharu.
This was about 40 minutes before the attack on
Pearl Harbor began. To be exact, the Malaya attack began
at 12:30 am on 8 December 1941 Malayan time (Kota Bharu), which at that time was UTC+7:30.
~7:02 AM:
Army radar station at Opana Point (Oahu, Hawaii) detects a large inbound formation. Report is misinterpreted by Lt. Tyler as a flight of
incoming U.S. bombers.
~7:30 AM:
Japanese attack on Midway Island began. (This was at Dec 7, 1941, ~6:30 AM Midway Island time.)
7:55 AM:
First wave of Japanese aircraft attacks Oahu. Battleship Row is hit. USS Arizona explodes at ~8:10 AM. Major airfields and naval
installations also bombed.
~8:00 AM:
Japanese landings began in Thailand (Songkhla, Patani). (This was at 8 Dec 1941, ~02:00 ICT Thailand time.)
8:50 AM:
Second wave of Japanese aircraft arrives and strikes remaining targets.
~9:45 AM:
Japanese air attack on Oahu ends. U.S. losses: 2,403 killed, 1,178 wounded, 21 ships damaged or destroyed, 188 aircraft destroyed.
~10:00 AM:
Japanese air raids on Singapore began. (This was at 8 December 1941 at 4:00 AM Singapore Time.)
Also: Japanese attack on Shanghai began. (This was at 4:00 AM, December 8, 1941 Shanghai Time.)
11.27 AM:
Japanese attack on Guam began. (This was at 8 Dec 1941, 08:27 ChST Guam Time.)
~12:00 Noon:
Delayed Western Union war warning finally reaches Hawaii. By this point, the attack is over.
~12:30 PM:
Japanese attack on Hong Kong began. (This was 8 Dec 1941, 07:30 HKT Hong Kong Time)
2:00 PM:
Japanese attack on Wake Island began. (This was noon (12:00 PM) on December 8, 1941 Wake Island time)
4:10 PM:
Japan issues its
Imperial War
Rescript declaring war on the United States and Britain -
eight and nine hours after attacking Hawaii (US) and Malaya (Great
Britain.).
16.35 PM:
Japanese attack on the Philippines began. (This was at 8 Dec 1941, 12:35–12:40 PHT (Clark Field main attack) Philippines Time.)
::: Japanese Operational Designations (Dec. 1941–42) :::
Operation AI (Japanese: A作戦, A Sakusen) refers specifically to the Imperial Japanese Navy’s carrier-based attack on
Pearl Harbor, executed on December 7, 1941. Contrary to some interpretations, Operation AI did not encompass Japan’s full
initial offensive across the Pacific and Southeast Asia; it was only the codename for the Pearl Harbor strike.
Other simultaneous assaults—on the Philippines, Guam, Wake Island, and elsewhere—were part of different plans, often grouped under the
army-led Southern Operation (南方作戦). The term “Operation AI” appears in postwar and some planning records, but it is not
fully certain whether it was the formally designated operational name used consistently in all official documents by the
Imperial Navy; other designations like “Hawaii Operation” (ハワイ作戦) and “Operation Z” were also used. Nonetheless, historians broadly
agree that the Pearl Harbor strike was treated as a distinct, navy-controlled operation and that “AI” was one of its internal designations.
Operation Z (Japanese: Z作戦, Zettsu Sakusen) refers to the codename used by Admiral Yamamoto Isoroku and his Combined Fleet
staff during the planning phase of the Pearl Harbor attack. The name was employed internally for secrecy and referenced Admiral
Tōgō’s famous “Z flag” signal from the 1905 Battle of Tsushima. While it is clear that “Operation Z” was used within Yamamoto’s inner
planning circle, it is not fully certain how widely this designation was known or used beyond the Combined Fleet staff—there is
little evidence that the broader Navy or Army commands used the term. Importantly, “Operation Z” must not be confused with
Japan’s 1944 Z Plan, a separate operational scheme aimed at defending the Marianas. Thus, when discussing “Operation Z,”
historical and contextual precision is essential.
Southern Operation (Japanese: 南方作戦, Nanpō Sakusen) refers to Japan’s large-scale, army-led campaign in Southeast Asia
launched concurrently with the attack on Pearl Harbor. Its strategic objectives were the conquest of British Malaya, Singapore,
the Dutch East Indies, and the Philippines, primarily to secure vital natural resources—especially oil, rubber, and tin. While
the Southern Operation was closely coordinated in timing with Operation AI, the two were distinct in geographic scope, objectives,
and command structure: Southern Operation was controlled primarily by the Imperial Army, whereas Operation AI was a naval
carrier strike in the Central Pacific. Historians consistently treat them as parallel but separate operations within Japan’s
broader December 1941 war opening.
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