Riddleberger, who controls Joey’s head, says the Handspring teachers during two weeks of intensive training challenged the puppeteers to continue working on “being” a horse: “We were even encouraged to surprise the actors from time to time.” His Twitter feed from April 9 documents some recommended reading  from that period.

Jones and Kohler say they like to go for a mixture of skills when they put together a team of puppeteers for Joey and for the full thoroughbred Topthorn, Joey’s even bigger pal.  Acrobatics, dance, physical and straight theater talents all are sought, along with specific heights and the ability to handle a heavy load.

Riddleberger learned his very physical approach to acting at New York University’s Tisch School of the Arts Experimental Theatre Wing. As the only puppeteer who’s visible always, he relies heavily on a first principle he learned from Handspring, called the “devotional state,” to cope with the exposure: “It means I put the puppet ahead of myself always. It is a challenge physically, because I have to be consciously very hard on myself to make sure I do not make a single move unless it is related to Joey and what the horse is doing. If I am going to take a step, Joey has to be part of that step.”

Patrick Osteen, who operates Joey’s front legs, spent some time around horses when he was young. His theatrical training had a classical component — he has choreographed fight scenes and played the gang leader Mercutio in Shakespeare’s “Romeo and Juliet.”

Krueger, who controls Joey’s back legs from inside the animal, has a strong acrobatic history. She recently puppeted the tail of the dragon Fafner in the Metropolitan Opera production of Wagner’s “Ring” Cycle. She also worked as a double, to help create the impression that Wagner’s Rhine Maidens could swim and that Valkyries could fly.

Inside Joey, Krueger takes her cues from Patrick Osteen, who is in front of her and cannot see her at all. “The first day that we galloped together in training,” Krueger says, “we worked on it for about ten minutes and I was already exhausted. It’s my job to keep the gait in proper form, so I’m sort of swimming behind Patrick, moving with his footsteps.  At first we were trying so hard we used a lot more muscular energy than we needed to, but eventually we became more efficient and relaxed, and it has definitely gotten easier.”

“War Horse” started life as a book, published in 1982 by Michael Morpurgo and intended for young readers. It was inspired by the tales he heard in Devonshire about the horses who died by the hundreds of thousands in World War I battlefields, and the people who cherished them. The book languished happily in bins and libraries until the mother of Tom Morris, a director then at the National Theatre in London, said he really ought to turn it into a play. 

Nick Stafford set about adapting the novel and that’s when the theater got in touch with Handspring gurus Jones and Kohler, who spent several years developing the horse prototypes.

How did they do it? Best to let them tell you. The two puppet masterminds are thoroughly entertaining in this 15-minute demonstration, directly below, which they gave at the 2011 TED conference devoted to “ideas worth spreading.”  Their talk details the breakthrough thinking required to create Joey and Topthorn. They had to advance their puppet technology from a smallish, hand-held hyenna, operated by two people, intended for viewing only from the front, to a 360-degree full-size horse, operated by three people and capable of  supporting a human rider. They would also need to simulate a gallop and other gaits, as well as allow for kicking and fighting with another full-size puppet horse in full stride.

Steven Spielberg, by his own account moved to tears at the London play, would next make a movie of the story. It opened on Dec. 25, 2011, without puppets, of course, but solving in a cinematic way the need to make Joey a fully expressive character.  Movie and stage play have enjoyed a certain synergy ever since, the one successful effort creating a ready made audience for the other.

Joey’s prolonged popularity and his rugged performance schedules came as something of a surprise to Jones and Kohler, who never imagined that they would need to build their cloth and reed creations to withstand years of wear and tear and thousands of performances. The routine takes a toll on performers, too.

“It’s the repetitions mostly,” says Osteen, who’s generally under Joey’s shoulders.  “The positions we maintain, and the very specific movements they require — such as the wrist movements in my case, and the legs in constant pliés,”  he explains, referring to the balletic knee bends. The puppeteers take their physical therapy seriously and are constantly monitoring for safer ways of doing things.

Since bionic therapy’s not readily available for Joey, Handspring has adjusted accordingly:  Nowadays, when they ship out a  new Joey, the package includes two necks, a couple of heads and eight legs, just in case.

Here’s the “War Horse” schedule into 2013: 

• U.S. national tour:  After Chicago — tickets here— “War Horse” moves on as follows:
  • Denver and Costa Mesa in January 2013
  • Tempe, then Seattle and Portland in February
  • Spokane, then St. Louis and Cincinnati in March
  • Cleveland in April
  • Tampa, then Fort Lauderdale as well as Fayetteville AR and Charlotte NC in May
  • Providence RI, then Minneapolis and Appleton WI in June.
• London:  Meanwhile, a sit-down production at New London Theatre in Drury Lane (home of the original “Cats” in 1981) continues.
• International: The UK and Ireland tour starts up in September 2013, and the first non-English language production, in Berlin, will begin in October 2013.