Waldo Williams was born in Haverfordwest, Pembrokeshire. His father, a primary school teacher from Pembrokeshire, spoke Welsh and his mother spoke English. In his early years he himself spoke only English.
In 1911 his father was appointed headteacher of the primary school at Mynachlog-ddu, Pembrokeshire and it was there that Waldo Williams learnt to speak Welsh. In 1915 Williams's father moved to be headteacher of Brynconin School, the primary school at Llandysilio, Pembrokeshire.
After attending the Grammar School at Narberth, Pembrokeshire he studied at the University College of Wales, Aberystwyth where he graduated in English in 1926. Afterwards he trained as a teacher and worked in various schools in Pembrokeshire, the rest of Wales and England. He also taught night classes organised by the Department of Extre-Mural Studies, University College of Wales, Aberystwyth.
Williams married in 1941, but his wife died in 1943, and he did not remarry.
During the Korean War he refused to pay his income tax on pacifist grounds. He continued his protest until the ending of compulsory military service in 1963. During his campaigning he was sent to prison.
He stood as a parliamentary candidate for Plaid Cymru in the Pembrokeshire constituency at the 1959 General Election when he won 4.32% (2.253) of the votes.
He died in 1971 at St. Thomas's Hospital, Haverfordwest, Pembrokeshire and is buried at Blaenconin Chapel burial ground in Llandysilio.

Williams's poetry shows many influences from William Wordsworth and Walt Whitman to Welsh hymns and the strict alliterative metres of traditional Welsh poetry, known as cynghanedd.
Williams belongs, first of all, to the Welsh tradition of the bardd gwlad (folk poet), a poet who served his locality by celebrating its life and people in verse.
But he was also a poet inspired by the mystic revelation he had as a youth about the unity of the whole of humankind. This revelation was realised in the cooperative and harmonious living he witnessed amongst the farming communities in the Preseli Hills and reflected in feelings of belonging, knowing, and a desire that people should live together in peace – constant themes in his poetry. It inspired some of his greatest poetry, including Mewn dau gae (In two fields) (1956), perhaps his greatest poem of all, which celebrates the very moment of this revelation.
Other well-known poems by Williams include Cofio (Remembering) (before 1936), Y tangnefeddwyr (The peacemakers) (1941), Preseli (1946), and Pa beth yw dyn?(What is it to be human?) (1952).

He was a conscientious objector to Word War II, and the horror of war was evident in his poems during this period –
Y Tangnefeddwyr (The Peacemeakers), which describes “Abertawe’n fflam” (“Swansea aflame”) is one which stays in the memory.

Y Tangnefeddwyr
Uwch yr eira, wybren ros, 
Lle mae Abertawe'n fflam.
Cerddaf adref yn y nos,
Af dan gofio 'nhad a 'mam.
Gwyn eu byd tu hwnt i glyw,
Tangnefeddwyr, plant i Dduw.
Ni châi enllib, ni châi llaid
Roddi troed o fewn i'w tre.
Chwiliai 'mam am air o blaid
Pechaduriaid mwya'r lle.
Gwyn eu byd tu hwnt i glyw,
Tangnefeddwyr, plant i Dduw.
Angel y cartrefi tlawd
Roes i 'nhad y deuberl drud:
Cennad dyn yw bod yn frawd,
Golud Duw yw'r anwel fyd.
Gwyn eu byd tu hwnt i glyw. 
Tangnefeddwyr, plant i Dduw.
Cenedl dda a chenedl ddrwg -
Dysgent hwy mai rhith yw hyn,
Ond goleuni Crist a ddwg
Ryddid i bob dyn a'i myn.
Gwyn eu byd, daw dydd a'u clyw,
Dangnefeddwyr, plant i Dduw.
Pa beth heno, eu hystâd,
Heno pan fo'r byd yn fflam?
Mae Gwirionedd gyda 'nhad
Mae Maddeuant gyda 'mam.
Gwyn ei byd yr oes a'u clyw, 
Dangnefeddwyr, plant i Dduw. 

The Peacemakers
Rose-red sky above the snow
Where bombed Swansea is alight,
Full of my father and mother I go,
I walk home in the night.
They are blest beyond hearing,
Peacemakers, children of God.
Neither, within their home, abuse
Nor slander could be found.
Mam would look for an excuse
For the biggest scoundrels round.
They are blessed beyond hearing,
Peacemakers, children of God.
It was the angel of poor homes
Gave my father two rich pearls:
Brotherhood the mission of man
God's largesse the invisible world.
They are blessed beyond hearing,
Peacemakers, children of God.
Nation good or nation bad
(So they taught) is fantasy.
In Christ's light is freedom had
For any man that would be free.
Blest, the day dawns that will hear them,
Peacemakers, children of God.
What is their estate tonight,
Tonight, with the world ablaze?
Truth is with my father yet,
Mother with forgiveness stays.
The age will be blest that hears them,
Peacemakers, children of God. 

Tangnefeddwyr was composed and arranged by Eric Jones

Born and brought up in Pontarddulais, Eric Jones was educated at Gowerton Boys’ Grammar School before graduating in Music from the University of Wales Cardiff. He started his teaching career in Llanelli, and subsequently became Head of Music and Creative Arts at Mynyddbach School, Swansea. After a period as Deputy Headmaster at Ysgol Gyfun Gwyr, he took up his present post as Headmaster of Ysgol Bro Myrddin, the Welsh medium comprehensive school at Carmarthen in 1997. He holds both the Licentiate and Fellowship diplomas of the Trinity College of Music, London, and a Masters degree of the Open University. He adjudicates frequently at the National Eisteddfod in vocal and composition competitions, and has been made an honorary member of the Gorsedd of Bards for his services to music in Wales. As a composer he has published five volumes of songs and a large number of choral works. He becomes President of Cor Meibion Pontarddulais having been the Accompanist of the choir for a period of eighteen years between 1973 and 1991.

For a rendition of Tangnefeddwyr by Morriston Rugby Club Choir and a graphic recolection of wartime Swansea follow this You Tube link

http://www.youtube.com/watch?v=8bRANQ4vwLA