Architecture studio WXCA has extended the Polish Army Museum in Warsaw, adding a low-lying wing with coloured-concrete walls that are imprinted with chevrons.

Named the South Building, the wing introduces another permanent exhibition space to the museum, as well as more areas to display its collection of over 300,000 artefacts.

The Polish Army Museum and South Building form a part of Warsaw Citadel, a 19th-century fortress in Poland's capital city.

According to WXCA, the design and colouration of the South Building draw on the existing brick buildings on the site, including the former barracks of the Royal Foot Guards.

"Warsaw Citadel is a pretty unique place – even though is located very close to the city centre, for the last 200 years the fortification has remained separated from the city and closed for residents and tourists," said WXCA partner Szczepan Wroński.

"The undergoing transformation is supposed to hand this place back to the people and create a place of culture, remembrance and recreation," Wroński told Dezeen.

The completion of South Building marks the end of the first phase of WXCA's extension of the museum, which will also include the yet-to-be-built North Building.

Together, the elongated, low-lying forms of the North and South Buildings will enclose the existing square on the site. The buildings were designed to evoke a disciplined battle array.

"Our concept reaches out to the 18th-century spatial arrangement of the Polish Royal Foot Guard barracks and centrally positioned square," said Wroński.

"The simple geometric and disciplined forms of the South and the North Buildings and their compact organisation from two sides of the square are reminiscent of a battle array layout in some way."

The main material used throughout the museum is concrete. It has a pink colouration that draws on the brick walls of the Warsaw Citadel.

To reduce the visual impact of the concrete, portions of the exterior and interior walls are imprinted with chevrons.

"We wanted to soften the monumentality of the building and create a surface for a sculptural play of light and shadow that changes depending on the time of day and thus alters the overall perception of the building," Wroński explained.

"The chevron pattern symbolically refers to military motives," he added. "We intended to make this subtle, indirect reference and let everyone have their own interpretation of the chevron form."

Once complete, the North Building will be of similar size to the South Building, but it will also contain an underground level. There will be an exhibition area, an auditorium and a shooting range for trying antique weapons.

Another element of the project is the creation of an underground parking lot, which is entered via a new gate to the Warsaw Citadel. This gateway punctures a historic brick wall and is topped by a green roof.

Other museums on Dezeen that are dedicated to army- and military-related collections are the stainless-steel National Museum of the United States Army by SOM in Virginia and the deconstructivist Museum of Military History in Dresden by Daniel Libeskind.

The photography is by Marcin Czechowicz.