WASHINGTON, April 17 (UPI) -- Charles Darwin was right -- at least for weapons systems: Principles of evolution and the struggle for survival of the fittest apply there all the time. Weapons systems have to keep evolving. And when they can't evolve any more -- they die.

Sometimes weapons evolution moves phenomenally quickly -- as was the case with aircraft design in World War II.

As late as 1942, the British Royal Navy was still using Fairy Swordfish biplanes of World War I capabilities in the war at sea -- and they worked. They sank half the battleships of the Italian navy in Taranto harbor in November 1940 and crippled the German Bismarck, the most deadly battleship afloat, in May 1941.

In February 1942, however, a wing of Swordfish biplanes was massacred by land-based German combat fighters when it tried to attack the German battle cruisers Scharnhorst and Gneisenau when they sailed up the English Channel in broad daylight -- defying and humiliating the Royal Navy in its home waters.

Yet within 3-1/2 years, the Luftwaffe -- the German air force -- was operating swept-wing, super-fast, twin-engine jet fighters, the famous Messerschmitt Me-262.

World War II began with the Polish army putting its faith in the strategic power of huge forces of horse cavalry -- something the Duke of Wellington and Gen. Ulysses S. Grant would both have regarded as insane in the previous century. It ended with Nazi Germany bombarding the British capital London with V-2 ballistic missiles and V-1 Flying Bombs, which were the progenitor of the modern cruise missile.

But between major wars, evolution in weapons systems tends to move a lot more slowly. Nobody dreamed that when the first Boeing B-52 Stratofortress bombers became operational with the U.S. Air Force in the 1950s that they would still be an effective front-line strategic weapons system more than half a century later. Even modern battleships never had operational lives half as long as that.

The Lockheed C-130 Hercules short landing and take-off transport aircraft has enjoyed an even longer career. Demand remains high in the U.S. Air Force and among allied nations for the new "J" variant, or mark, the Super-Hercules, which Lockheed Martin (NYSE:LMT) continues to manufacture today.

But even the B-52 and the C-130 pale in longevity compared with Russia's Tupolev Tu-95 Bear. In its airframe -- a clear copy of the great Boeing long-range strategic bombers of the late 1940s and early 1950s that began with the B-47 and culminated in the B-52 -- the Tu-95 is less advanced in its design than any of them as it is powered not by jet turbines at all, but only by turbo-prop engines. Yet the propeller-driven Tu-95, relatively vulnerable and slow though it is, is so useful to the Russian air force that there are currently plans to keep it on operational duty until 2040.

Of course, none of these aircraft is the same today as when they first flew in the 1950s. Their continual upgrading or "evolution" continues as new weapons systems, electronic counter-measures and even engines replace old ones on the basic airframe.

In land war, the rate of evolution, or adaptation, to changing combat circumstances is far faster than in the air, yet the basic principles of combat remain the same.

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