TEXT: www.games-workshop.com
  A single Ork is a formidable adversary, muscular and violent
  with a resilient physiology and an unquenchable lust for
  war. A single Ork is, however, rarely encountered, for when
  Orks go to battle they do so in countless thousands. This is
  when the Orks are at their most dangerous. When they are
  part of a great Waaagh! ‘Uge mobz of Ork Boyz gather, for
  every Ork gunned down, three step forward to take its
  place. Their numbers are so vast that they resemble a green
  ocean. Wave after wave of Ork Boyz comes crashing down
  on enemy positions, quite literally a green tide that rises up
  and sweeps away all before it.
  Any Orks in the vicinity of such a stampede get caught up
  in the violent charge. Some have no choice and must join
  the rush or else get crushed, but more often than not the
  Boyz find themselves tagging along by instinct. Something
  about so many Orks charging towards the enemy triggers
  something in the Ork psyche – after all, wherever they’re
  going, so many Boyz can’t be wrong! Even Orks that do
  run away quickly turn back and are once again swallowed
  up by the horde. In this way the ranks of the horde swell as
  the charge gathers momentum, overwhelming any
  resistance that dares oppose the might of the Greenskins.
  THE GREEN TIDE
  POINTS: 75 + MODELS
  FORMATION:
  A single unit consisting of a Warboss leading an ‘Uge mob.
  An ‘Uge mob is identical to a normal Ork Boyz mob and has
  all the same options with the exception that the unit numbers
  at least 100 models and may include a mixture of Boyz armed
  with sluggas and choppas and Boyz with shootas. There is no
  maximum size this unit may reach. The Warboss may not leave
  this unit. The entire formation goes to battle on foot and as
  such may not ride in any troop transports. The Warboss may
  not take a Warbike.
  SPECIAL RULES
  Stampede: Nothing can stand in the way of so many stomping Orks. The formation has the Move Through Cover rule to
  represent the momentum the Boyz have barrelling through terrain. In addition the sheer number of Orks whips the Boyz into a
  constant state of bloodlust. The formation may call upon the Waaagh! each and every turn. If the rest of the army also calls upon
  the Waaagh! then the Green Tide may roll two dice and pick the highest when determining the extra distance moved.
  Follow Me Ladz!: Nearby mobs tend to be caught up and swept along when such a large horde of Orks stampedes across the
  battlefield. Any Ork Boyz mob that falls back within 48” of the Warboss is removed and immediately placed in the unit led by the
  Warboss (or if by some miracle ALL his Boyz have been shot up, they form a unit which he then leads). The models are placed such
  that they are in unit coherency and are no closer to the enemy than the Warboss. There is no limit to the size this unit may reach.
  THE GREEN TIDE
  Warboss Gitstomp
  Gitstomp’s Ladz
  An adjutant directed the General’s gaze to the south, where the Orks
  were said to be mustering after planetfall. Adjusting the focus of his
  magnoculars, Titus gave a gasp of disbelief. There were the Orks. The
  shapes of a dozen Gargants jutted up from the undulating ash
  wastes, a swarm of similar vehicles surrounding them. But it was not
  this that had given Titus such a shock. For miles in every direction
  around the Gargants, the ash desert was green; a sea of Orks so
  massive that the mind refused to acknowledge the possibility. Titus
  examined his own forces once more, his heart in his throat.
  “Emperor’s mercy,” he whispered to himself, “I pray I have enough
  men to face that!”
  © Games Workshop Limited 2007. Games Workshop, Warhammer, Warhammer 40,000, Apocalypse are ©, TM and/or ® Games Workshop Limited 2007. All rights reserved.
  
SOURCE: textdata/thevault/Warhammer/40k/1st-8th Editions (Prior)/5th Edition (2008)/Apocalypse Datasheets/40k 5e - Ork - The Green Tide.pdf