This simple song was Brel's first major hit, reaching #3 on the international charts. It became his signature song, and strains of it were heard as the curtains closed on his farewell performance. The songs begins with the love of two for each other, then extends to all mankind addressing major issues of poverty and war, unlike the conventional romantic chansons of its day. Brel was still under the influence of Jesuit training at he time he wrote this. By the '60s there were a lot of anti-war songs, and similar messages of love and peace, but this is the earliest I can think of.
The Mort Shuman adaptation for Jacques Brel is Alive and Well performs the song twice, with a full cast reprise for the finale.