Guerre di meraviglie

EVERY three seconds the anti-aircraft gun crew was slamming another shell at the target. At 20,000 feet the towing airplane was a tiny speck and the silk sleeve target, half a mile behind the plane, was invisible to the unaided eye. But even if the target had been visible the eighteen men who were serving the three-inch gun and the three other gun crews of the battery were too busy to watchit. Studying the shell bursts through his glasses, an observer on the other side of the hill called a correction into his field telephone. At the director station near the guns a man turned a pointer of the mechanical brain that was directing the fire,and the new data went out by electric cable to the gun crews. An anti-aircraft battery can blanket a section of sky with 100 shells a minute. One shell is enough if it hits the target, but the target is so small, so high, and is moving so fast that an effective hit would be sheer luck if it were not for the mechanical director that tells the gunners where to aim. The director is a $25,000 mathematics machine that digests such information as the altitude and speed of the target, the wind, barometric pressure, and temperature of the air and powder, and from these data determines the point in space at which a shell should burst to score a hit. The firing data are automatically transmitted to the guns where the crews “match dials” to keep the guns trained continuously in front of the target. Defense against airplanes has become a vital part of harbor defense. Harbors have to defended to maintain them as safe havens for merchant and naval vessels and to prevent an enemy irom using them as landing places. Our important harbors on each coast are fortified against attack by surface vessels, but even the powerful sixteen-inch rifles of the forts are vulnerable from the air. The first thing an invader would do before attacking with his fleet would be to bomb the big guns. Against such a possibility mobile anti-aircraft batteries of the Coast Artillery are constantly practicing. At Fort MacArthur, overlooking Los Angeles harbor, the anti-aircraft batteries of the 63rd Coast Artillery conduct day and night practice against towed aerial targets. Shrapnel and high-explosive shells with an effective radius of 100 yards are fired at targets that are towed straight to simulate the sighting run of a bomber, and against targets that are dived or moved in sinuous courses in efforts to spoil the aim. Loaded on their heavy trucks, the batteries can move along the highways at ordinary road speeds and the six-wheel-drive trucks can carry guns and equipment across rough terrain to get into position. Part of the present rearmament program of the United States includes large numbers of anti-aircraft guns of heavier caliber with greater range and hitting power than the present equipment. This will help compensate for the advantage that bombers at present seem to enjoy over ground forces. An anti-aircraft battery and a bomber cost about the same and the bombers have the advantage of being able to select one out of many possible targets while the batteries on the ground are impotent against aircraft except those that cross near by. In a recent maneuver over the Panama Canal a fleet of naval bombers, dropping flares and dummy bombs instead of real projectiles, made a simulated night attack at 8,000 feet, simultaneously striking at half a dozen points. The invaders won a paper victory and in theory several of the locks were destroyed, due to the lack of adequate numbers of defending guns. A properly organized bombing raid includes flights of low-flying attack planes whose mission it is to put the anti-aircraft batteries out of action with machine-gun fire or bombs, or to curtain the guns with smoke screens. The attack planes are fought off with fifty-caliber machine guns and with heavier thirty-seven-millimeter guns that fire clips of one-pound explosive shells. In their camouflaged locations, the anti-aircraft guns play ’possum until the bombers are in range, and even if smoke screens have been laid the guns can fire through the smoke effectively. The spotters at the director and not the men at the guns have to see the target, so the director is often moved some distance away, outside the area where smoke screens are apt to be laid. An offset adjustment is made to the mechanism, and the firing data remain as accurate as if the director were alongside the guns. On night raids the oncoming bombers are first detected by big mechanical ears and then searchlights are pointed to the same section of the sky. The 800,000,000-candlepower beams pick up and follow the planes so that the men at the stereoscopic height-finding device and the spotters at the director can track them. Instead of depending on armored forts to defend its harbors the United States uses fortified areas in which fixed and mobile guns are trained to cover the channels and adjacent ocean. The Gibraltar-like headlands of San Francisco and Los Angeles harbors are fortified and in these cases the ammunition storage rooms, machine shops, and the plotting and control rooms are buried below ground. Besides the anti-aircraft guns, a thoroughly fortified area contains three and six-inch rapidfire guns that are effective against light small craft and destroyers, long-range high penetration eight and ten-inch rifles to be used against light armored cruisers, and mortars and rifles ranging from twelve to sixteen inches that are adequate against heavily armored battleships. Army experts figure that one gun on shore is equal to ten guns of similar caliber and range on board ship. A gun emplacement is a much smaller target than a ship and it would take a direct hit to put a gun out of action while a hit on any part of a ship is apt to cripple it. Another reason why the shore batteries have the edge is that they can be aimed simply and accurately while the gunners afloat must reckon with the speed, roll and pitch of their ships in aiming their guns. When an airplane is used for fire control the pilot carries a map on which the adjacent ocean is divided into 1,000-foot squares. He locates the target in one of the squares and radios the number of the square back to the plotting room. One shot is fired at the middle of the same square and the pilot, watching where the shell hits, radios down a correction. Coast defense is a joint duty of the army and navy, and the work of the Coast Artillery regiments is coordinated with the defense tactics of the navy and the Army Air Corps. The navy lays mines offshore and the Coast Artillery lays the strings of mines that protect the narrow entrances of harbors, Instead of always exploding upon contact with a hull, such mines are controlled from shore. Thus friendly vessels can pass in and out unscathed. Harbors are protected also by underwater anti-submarine nets. The Coast Artillery operates railroad rifles that in case of emergency would be moved to positions commanding beaches where attempts to put landing parties ashore might be made. Practically unimproved since the World War, our coast defenses on both sides of the continent and in Alaska and Panama are soon to be modernized by increasing the number of fortified areas and the number of guns in each area, and by building bombproof and gasproof shelters for the gun crews.