Okinawa was the bloodiest battle of the Pacific War. The most complete tally of deaths during the battle is at the Cornerstone of Peace monument at the Okinawa Prefecture Peace Park, which identifies the names of each individual who died at Okinawa in World War II. As of 2010, the monument lists 240,931 names, including 149,193 Okinawan civilians, 77,166 Imperial Japanese soldiers, 14,009 American soldiers, and smaller numbers of people from South Korea (365), the United Kingdom (82), North Korea (82) and Taiwan (34).
The numbers correspond to recorded deaths during the Battle of Okinawa from the time of the American landings in the Kerama Islands on March 26, 1945, to the signing of the Japanese surrender on September 2, 1945, in addition to all Okinawan casualties in the Pacific War in the fifteen years from the Manchurian Incident, along with those who died in Okinawa from war-related events in the year before the battle and the year after the surrender. 234,183 names were inscribed by the time of unveiling and new names are added each year. Forty thousand of the Okinawan civilians killed had been drafted or impressed by the Japanese army and are often counted as combat deaths.
The name comes from the medieval-Latin term balneum (or balineum) Mariaeliterally, Mary's bathfrom which the French bain de Marie, or bain-marie, is derived. The device's invention has been popularly attributed to Mary the Jewess, an ancient alchemist. However, the water bath was known many centuries earlier (Hippocrates and Theophrastus).
Before the advent of long-range fighter escorts, B-17s had only their .50 caliber M2 Browning machine guns to rely on for defense during the bombing runs over Europe. As the war intensified, Boeing used feedback from aircrews to improve each new variant with increased armament and armor. The number of defensive guns increased from four 0.50 in (12.7 mm) machine guns and one 0.30 in (7.62 mm) nose machine gun in the B-17C, to thirteen 0.50 in (12.7 mm) machine guns in the B-17G. But because the bombers could not maneuver when attacked by fighters, and needed to be flown straight and level during their final bomb run, individual aircraft struggled to fend off a direct attack.
A 1943 survey by the USAAF found that over half the bombers shot down by the Germans had left the protection of the main formation. To address this problem, the United States developed the bomb-group formation, which evolved into the staggered combat box formation where all the B-17s could safely cover any others in their formation with their machine guns, making a formation of the bombers a dangerous target to engage by enemy fighters. Luftwaffe fighter pilots likened attacking a B-17 combat box formation to encountering a fliegendes Stachelschwein, "flying porcupine", with dozens of machine guns on a combat box formation of bombers, aimed at them from almost every direction. However, the use of this rigid formation meant that individual aircraft could not engage in evasive maneuvers: they had to fly constantly in a straight line, which made them vulnerable to the German flak. Moreover, German fighter aircraft later used the tactic of high-speed strafing passes rather than engaging with individual aircraft to inflict damage with minimum risk.
As a result, the B-17s' loss rate was up to 25% on some early missions (60 of 291 B-17s were lost in combat on the second Raid on Schweinfurt), and it was not until the advent of long-range fighter escorts (particularly the North American P-51 Mustang) resulting in the degradation of the Luftwaffe as an effective interceptor force between February and June 1944, that the B-17 became strategically potent.
The B-17 was noted for its ability to absorb battle damage, still reach its target and bring its crew home safely. Wally Hoffman, a B-17 pilot with the Eighth Air Force during World War II, said, "The plane can be cut and slashed almost to pieces by enemy fire and bring its crew home." Martin Caidin reported one instance in which a B-17 suffered a midair collision with a Focke-Wulf Fw 190, losing an engine and suffering serious damage to both the starboard horizontal stabilizer and the vertical stabilizer, and being knocked out of formation by the impact. The B-17 was reported as shot down by observers, but it survived and brought its crew home without injury. Its toughness was compensation for its shorter range and lighter bomb load compared to the B-24 and British Avro Lancaster heavy bombers. Stories circulated B-17s returning to base with tails shredded, engines destroyed and large portions of their wings destroyed by flak. This durability, together with the large operational numbers in the Eighth Air Force and the fame achieved by the Memphis Belle, made the B-17 a key bomber aircraft of the war. Other factors such as combat effectiveness and political issues also contributed to the B-17's success.
The B-17 design went through eight major changes over the course of its production, culminating in the B-17G, differing from its immediate predecessor by the addition of a bombardier-operated, remotely controlled chin turret with two .50 in (12.7 mm) caliber M2 Browning machine guns under the nose, also fitted to the final eighty-six production aircraft of the B-17F-DLs built by Douglas, after being first tried in May 1943 as part of the increased armament system of the YB-40. This eliminated the B-17's main defensive weakness in head-on attacks.