How was the Easter Rising rebellion both terrible and beautiful?

Too long a sacrifice

Can make a stone of the heart.

O when may it suffice?

That is Heaven’s part, our part

To murmur name upon name,

As a mother names her child

When sleep at last has come

On limbs that had run wild.

What is it but nightfall?

No, no, not night but death;

Was it needless death after all?

For England may keep faith

For all that is done and said.

We know their dream; enough

To know they dreamed and are dead;

And what if excess of love

Bewildered them till they died?

I write it out in verse -

MacDonagh and MacBride

And Connolly and Pearse

Now and in time to be,

Wherever green is worn,

Are changed, changed utterly:

A terrible beauty is born.

- from William Butler Yeats’ Easter 1916