The loyalist marching season kicks off in Northern Ireland at a time of growing tensions, driven by discontent over Brexit, that is also causing divisions within the largely Protestant unionist community.

DERRY, Northern Ireland — The curbs are painted the blue, red and white of Britain’s Union Jack in the Fountain public housing development, the only Protestant enclave in this part of Derry, Northern Ireland. The ashes of a bonfire fueled with the tricolor flag of neighboring Ireland lay in a central square.

Along these narrow streets, bands from the Protestant community marched on Monday to mark July 12, a commemoration of a centuries-old military victory of a Protestant king over a Catholic one.

Such marches are a longstanding annual event in Northern Ireland, but the tensions growing over changes that Brexit has wrought in the region are casting the parades in a new light. There has been sporadic violence in recent months, and fears that the tense climate could threaten the landmark 1998 Good Friday Agreement that ended decades of sectarian strife and halted a 30-year conflict in Northern Ireland.

Across the region last weekend, bonfires blazed ahead of the parades, as towers of teetering pallets were set alight, casting a flickering orange glow on the faces of onlookers who gathered for street parties. This year, there are two additional dynamics at play — the centenary of the partition of Ireland that established Northern Ireland, and ongoing discontent with the post-Brexit trade arrangements for the region, known as the Northern Ireland protocol, that have heightened long-dormant tensions.