Direct proof of use
The MOWAG Piranha's documented use in the 2003 Iraq War centers on Denmark's Iraq contingent. The Danish Armed Forces state that Denmark had used Piranha 3 vehicles since the mid-1990s and that the type had been deployed in Iraq, Afghanistan, and the Balkans.
A Danish Armed Forces article from August 3, 2007 gives incident-level proof of Piranha use during the final withdrawal drive from Iraq. It describes the Danish reconnaissance squadron's Piranha vehicles leaving Camp Einherjer, escorting a convoy of heavy trucks toward Kuwait, one Piranha being hit by a roadside bomb, and the commander's Piranha turning back to assess the damage.
Sources: Forsvaret Piranha 5 Materiel Page, Forsvaret Spejdernes Farvel Til Irak
Dated service record
Denmark's DANCON/Irak mission began after a parliamentary decision on May 15, 2003 to send about 380 troops to southern Iraq under the British-led Multinational Division South East. The Danish Armed Forces mission history says the first Danish main force reached Kuwait in early June 2003 and took responsibility for an area near Al Qurnah, north of Basra, on June 12.
The same Danish Armed Forces mission history records a Piranha image from October 2004 in the Iraq mission page's media set, and it describes Danish battalion tasks that included patrols, security duties, escort work, monitoring, and cooperation with Iraqi security forces. By February-August 2007, Iraq Hold 9 was the last Danish rotation in the southern-Iraq area; the separate 2007 withdrawal article identifies Piranha vehicles in the reconnaissance squadron convoy that left Iraq for Kuwait.
Sources: Forsvaret DANCON Iraq Mission, Forsvaret Spejdernes Farvel Til Irak
Role in Iraq
The sourced record supports a convoy, patrol, and protected-mobility role for Danish Piranha vehicles rather than a separate heavy-weapons role. Forsvaret's Iraq mission page describes Danish battalion security tasks in the Basra region, while the 2007 article places Piranhas in a convoy escorting battalion goods and personnel out of Iraq.
The August 2007 roadside-bomb incident also illustrates why the Piranha appears in this conflict as a force-protection and mobility system. The article reports damage to the road and a truck, while Piranha vehicles continued to function as command and convoy vehicles during the withdrawal drive.
Sources: Forsvaret DANCON Iraq Mission, Forsvaret Spejdernes Farvel Til Irak