  Nash-Williams proved in 1960 that a finite graph admits a $k$-arc-connected
orientation if and only if it is $2k$-edge-connected, and conjectured that the
same result should hold for all infinite graphs, too.
  Progress on Nash-Williams's problem was made by C. Thomassen, who proved in
2016 that all $8k$-edge-connected infinite graphs admit a $k$-arc connected
orientation, and by the first author, who recently showed that
edge-connectivity of $4k$ suffices for locally-finite, 1-ended graphs.
  In the present article, we establish the optimal bound $2k$ in
Nash-Williams's conjecture for all locally finite graphs with countably many
ends.
