bulwark

bulwark \BUL-wurk; -wawrk\, noun, verb:

1. to defend or protect, serve as a bulwark; shelter
2. a person, thing, or concept that is a defense or protection
3. an embankment of earth or other material used as a defense against a threat; rampart
4. the sides of a ship extending like a fence above the deck level

The French eventually prevailed, and Asher and his ally Alex were kicked up north to the town of Siem Reap, where they helped reconstruct the earthquake-damaged Elephant Wall, an infuriatingly complicated Khmer bulwark that had fallen into several hundred pieces some centuries ago.
-- Robert Bingham, Lightning on the Sun

Originally a set of largely structural guarantees applying only against the federal government, the Bill has become a bulwark of rights against all government conduct.
-- Akhil Reed Amar, The Bill of Rights: Creation and Reconstruction

The country has overwhelming importance to America as a strategic ally in a highly volatile Islamic region; indeed, Washington is counting on it to be a bulwark against the spread of Islamic fundamentalism into Europe.
-- Jeffrey E. Garten, The Big Ten: The Big Emerging Markets and How They Will Change Our Lives

For Laura's mother the church, in addition to what spiritual significance it possessed, stood out as a bulwark of civilization in the midst of a still forming, rough frontier culture.
-- John E. Miller, Becoming Laura Ingalls Wilder: The Woman Behind the Legend

Today we bulwark an older, liberal-Christian Europe against newer atheistic totalitarian forces.
-- Daniel J. Boorstin, We, the People, in Quest of Ourselves, New York Times, 20207

c.1418, from Middle Dutch bulwerke or Middle High German bolwerc, from bole "plank, tree trunk" + werc "work." The figurative sense dates from 1577.