:00:00. > :00:00.Jenny here with a special interview with the Prime Minister on the way,
:00:07. > :00:13.plus a look at the tactics that helped win World War One.
:00:14. > :00:15.First, the Prime Minister, David Cameron, has told Newsround
:00:16. > :00:19.how difficult it was to explain World War One to his own children.
:00:20. > :00:23.Lights were turned off across the UK last night to mark 100 years
:00:24. > :00:26.since Britain became involved in the conflict,
:00:27. > :00:31.And yesterday, at a special ceremony in Belgium, Ricky spoke to
:00:32. > :00:41.Mr Cameron about the lessons we should learn from the Great War.
:00:42. > :00:47.How do you explain what happened all those years ago to your own
:00:48. > :00:51.children? I find it very difficult, but I'm working very hard at it,
:00:52. > :00:57.explaining the First World War and the Second World War. You have to
:00:58. > :01:00.explain the scale, which is hard for people to comprehend, but that is
:01:01. > :01:05.important. I think you also have to explain what the war was about. When
:01:06. > :01:09.we look at the graves of these people here, they were killed in the
:01:10. > :01:13.very first days of the war, and they came here because they believed that
:01:14. > :01:18.a country in Europe, Belgium, was being overrun by the Germans, and
:01:19. > :01:23.they were fighting against the domination of the continent by one
:01:24. > :01:28.power. They believed it was a just war, and I think we need to explain
:01:29. > :01:31.that to our children as well as the scale of the massacre and the
:01:32. > :01:36.important things that happen. And what have you taken from today so
:01:37. > :01:41.far? I think it is important to commemorate those who gave their
:01:42. > :01:46.lives and to learn the lessons of finding other ways than war to solve
:01:47. > :01:49.our problems. But it is also important member of the ways that
:01:50. > :01:53.the First World War changed our world. Some bad ways, new ways to
:01:54. > :01:57.kill each other, but some good ways, advances in medicine, votes for
:01:58. > :01:57.women. Some good things came out of what happened. Thank you for talking
:01:58. > :01:59.to us. Pleasure. There's loads more information
:02:00. > :02:01.on World War One on the Newsround website, including the story
:02:02. > :02:03.of 14-year-old soldier Horace. During the conflict, soldiers like
:02:04. > :02:06.him spent a lot of time in trenches, ditches dug in the ground
:02:07. > :02:09.for soldiers to live and fight in. In the next of our special reports,
:02:10. > :02:26.Ricky's been to find out about Sanctuary Would, where we are right
:02:27. > :02:30.now, would have been bombarded by the Germans, who would have tried to
:02:31. > :02:34.get the Britons down below in the trenches, they would have tried to
:02:35. > :02:38.bomb them. You can see the these guys here today, the holes in the
:02:39. > :02:42.ground where some of the explosives went off. So this is what life would
:02:43. > :02:47.have been like for the soldiers who were in the trenches. They would
:02:48. > :02:53.have been very wet, very muddy, and endless network of corridors that
:02:54. > :02:56.were built and propped up with corrugated sheets of metal. And it
:02:57. > :03:00.would not have been a very pleasant place to be. It was the scene of one
:03:01. > :03:03.of the biggest air battles in the First World War, with 90 aircraft
:03:04. > :03:07.fighting over here. Somebody described it like a swarm of bees.
:03:08. > :03:12.The main idea here in these trenches was, this was a place of sanctuary
:03:13. > :03:16.where you could come, and there were defences all around here. Very rare
:03:17. > :03:19.to see a circular defence. But the German front line was over there,
:03:20. > :03:23.and also the scene of this word would be seen at the first plane
:03:24. > :03:29.throw attack. Liquid fire, the Germans called it. Dash-macro
:03:30. > :03:32.flame-thrower. This place was under shelves all the time, so it was a
:03:33. > :03:36.hard place to be. You can see a sniper play, and sometimes no man's
:03:37. > :03:41.land was so close that the centuries had to hide behind that metal plate.
:03:42. > :03:47.They couldn't just stick their heads up, or they would get shot. You can
:03:48. > :03:51.look through a little keyhole and cover it up again to make sure the
:03:52. > :03:55.Germans are not coming. So we are talking about people fairly close to
:03:56. > :03:59.here as well. Commanding high ground was crucial. Bromberg here, you can
:04:00. > :04:04.see the enemy. Here in France, soldiers fought and died at this
:04:05. > :04:08.very spot. But it was the Canadian Army who achieved what the French
:04:09. > :04:15.and the Brits could not do during a snowstorm on Easter Sunday, 1917.
:04:16. > :04:19.The Canadian Corps in April 1917, with four divisions in line on a
:04:20. > :04:25.front of four miles, attacked and captured this rich. We remember
:04:26. > :04:28.their spirit and fight on. As the war progressed and technology
:04:29. > :04:32.advanced, tactics began to change. Poisonous gas was used for the very
:04:33. > :04:37.first time, and tunnelling, burying explosives under the enemy, would
:04:38. > :04:42.also cause mass casualties. The British when they planned the
:04:43. > :04:46.attack, knew that this area would be a very tough not to crack. To give
:04:47. > :04:51.the troops the best possible chance, they dug underneath the ground, and
:04:52. > :04:55.in the tunnels, they tried to get right underneath the German
:04:56. > :04:59.positions and make large caverns where they would plant explosives
:05:00. > :05:02.that would go off literally just before the attack, and so when the
:05:03. > :05:07.British troops attack, there would be nothing left to defend against
:05:08. > :05:15.them. And this was the result. A crater
:05:16. > :05:20.that is 21 metres deep. They used ?60,000 worth of explosive to create
:05:21. > :05:24.this giant hole, and when the explosion was me, it was so loud,
:05:25. > :05:29.they could hear it all the way in London, 150 miles away. It is very
:05:30. > :05:38.difficult to imagine, but I suppose the best way to try and understand
:05:39. > :05:42.this is imagine 60,000 pounds, each one representing a pound bag of
:05:43. > :05:47.sugar, under the earth, and when that was exploded, what that would
:05:48. > :05:48.create was a lasting geography changing monument that still exists
:05:49. > :05:52.to this day. We'll be back with
:05:53. > :05:55.the day's other news at 9:30.