05/08/2014 Newsround

Jenny here with a special interview with the Prime Minister on the way,

plus a look at the tactics that helped win World War One.

First, the Prime Minister, David Cameron, has told Newsround

how difficult it was to explain World War One to his own children.

Lights were turned off across the UK last night to mark 100 years

since Britain became involved in the conflict,

And yesterday, at a special ceremony in Belgium, Ricky spoke to

Mr Cameron about the lessons we should learn from the Great War.

How do you explain what happened all those years ago to your own

children? I find it very difficult, but I'm working very hard at it,

explaining the First World War and the Second World War. You have to

explain the scale, which is hard for people to comprehend, but that is

important. I think you also have to explain what the war was about. When

we look at the graves of these people here, they were killed in the

very first days of the war, and they came here because they believed that

a country in Europe, Belgium, was being overrun by the Germans, and

they were fighting against the domination of the continent by one

power. They believed it was a just war, and I think we need to explain

that to our children as well as the scale of the massacre and the

important things that happen. And what have you taken from today so

far? I think it is important to commemorate those who gave their

lives and to learn the lessons of finding other ways than war to solve

our problems. But it is also important member of the ways that

the First World War changed our world. Some bad ways, new ways to

kill each other, but some good ways, advances in medicine, votes for

women. Some good things came out of what happened. Thank you for talking

to us. Pleasure. There's loads more information

on World War One on the Newsround website, including the story

of 14-year-old soldier Horace. During the conflict, soldiers like

him spent a lot of time in trenches, ditches dug in the ground

for soldiers to live and fight in. In the next of our special reports,

Ricky's been to find out about Sanctuary Would, where we are right

now, would have been bombarded by the Germans, who would have tried to

get the Britons down below in the trenches, they would have tried to

bomb them. You can see the these guys here today, the holes in the

ground where some of the explosives went off. So this is what life would

have been like for the soldiers who were in the trenches. They would

have been very wet, very muddy, and endless network of corridors that

were built and propped up with corrugated sheets of metal. And it

would not have been a very pleasant place to be. It was the scene of one

of the biggest air battles in the First World War, with 90 aircraft

fighting over here. Somebody described it like a swarm of bees.

The main idea here in these trenches was, this was a place of sanctuary

where you could come, and there were defences all around here. Very rare

to see a circular defence. But the German front line was over there,

and also the scene of this word would be seen at the first plane

throw attack. Liquid fire, the Germans called it. Dash-macro

flame-thrower. This place was under shelves all the time, so it was a

hard place to be. You can see a sniper play, and sometimes no man's

land was so close that the centuries had to hide behind that metal plate.

They couldn't just stick their heads up, or they would get shot. You can

look through a little keyhole and cover it up again to make sure the

Germans are not coming. So we are talking about people fairly close to

here as well. Commanding high ground was crucial. Bromberg here, you can

see the enemy. Here in France, soldiers fought and died at this

very spot. But it was the Canadian Army who achieved what the French

and the Brits could not do during a snowstorm on Easter Sunday, 1917.

The Canadian Corps in April 1917, with four divisions in line on a

front of four miles, attacked and captured this rich. We remember

their spirit and fight on. As the war progressed and technology

advanced, tactics began to change. Poisonous gas was used for the very

first time, and tunnelling, burying explosives under the enemy, would

also cause mass casualties. The British when they planned the

attack, knew that this area would be a very tough not to crack. To give

the troops the best possible chance, they dug underneath the ground, and

in the tunnels, they tried to get right underneath the German

positions and make large caverns where they would plant explosives

that would go off literally just before the attack, and so when the

British troops attack, there would be nothing left to defend against

them. And this was the result. A crater

that is 21 metres deep. They used ?60,000 worth of explosive to create

this giant hole, and when the explosion was me, it was so loud,

they could hear it all the way in London, 150 miles away. It is very

difficult to imagine, but I suppose the best way to try and understand

this is imagine 60,000 pounds, each one representing a pound bag of

sugar, under the earth, and when that was exploded, what that would

create was a lasting geography changing monument that still exists

to this day. We'll be back with

the day's other news at 9:30.