1 meter
A military dugout is a pit or deep trench dug into the ground and used as a shelter.
Not exactly. Anderson shelters were intended to be semi submerged in back gardens. A hole about two foot deep was dug in the earth and the semi-circular corrugated iron shelter was placed in the hole. The excavated soil was then placed on top of the shelter to give it extra protection. The main problem, because it was partially underground, was flooding.
If you dug a hole 592 kilometers deep, you would reach the upper part of the Earth's mantle, which extends from the crust to about 2,900 kilometers beneath the surface. You would not reach the Earth's outer core, which starts at a depth of about 2,900 kilometers.
Trench
No one never dug a hole that deep before
That depends how deep the well was dug or drilled.
in a den that is dug in the ground
The grey wolf's shelter is usually a den dug in the ground on a hillside or it can be underground with a tunnel about three meters long leading to where the cubs are.
There were various types of shelter constructed. The most popular was the Anderson shelter which consisted of curved sections of corrugated tin bolted together and half buried. The top was covered with a thick layer of earth. They were very strong but couldn't stand a direct hit. Larger shelters were often constructed from concrete and brick though deep shelters used at military sites along the south coast were dug from the chalk cliffs and then lined with corrugated tin. Another type of shelter (IIRC the Morrison shelter) was a steel table that you could shelter underneath indoors that would protect against falling debris.
The fox dug a deep hole for her puppies.
This depends on how deep the hole is dug, for the out house. If it's dug too deep then the contents may seep into the water level and end up in a near by lake.
Another word for a deep ditch that is dug around a castle is a moat. You could call it a trench, or you could fill it full of water and call it a moat.