WASHINGTON, April 9— The march on Baghdad exemplifies 21st-
century warfare, allied commanders and outside military experts
say: swift, agile and decisive, employing overpowering
technology to bring relentless violence to bear in many places
at once.  ''The superior technology we now possess is, perhaps,
the most obvious difference between the gulf war and the present
conflict,'' Vice President Dick Cheney, who was the secretary of
defense 12 years ago, said today.  In the 1991 Persian Gulf war,
only one combat aircraft in five could drop a bomb on a target
sighted by a laser; today they all can, Mr. Cheney said.  Only 9
percent of the weapons dropped in the 1991 war were precision-
guided; for this war, air combat officials based in Saudi Arabia
said today that a total of 15,000 precision-guided munitions and
7,500 unguided bombs had been dropped thus far. When added to
more than 750 cruise missiles, the percentage of precision
munitions used in the war is 68 percent.  Then, a strike might
happen two days afte