The lighting of the candle on the second Sunday of Advent marks Jesus' forthcoming birth as the promise of peace on earth.

Jesus is the 'Prince of Peace'.

One of the hallmarks of the Christmas story is when the angels appear to the shepherds and proclaim:

'Glory to God in the highest and on earth peace to all men
on whom his favour rests.' (Luke 2:14)

Foreseen earlier in the OT by the prophet Isaiah:

'For to us a child is born. And he will be called
Wonderful Counsellor, Mighty God, Everlasting Father,
Prince of Peace.' (Isaiah 9:6)