Public duties are performed by military personnel, and usually have a ceremonial or historic significance rather than an overtly operational role.
The Wachregiment Berlin was founded in early 1921. In addition to genuine security duties, the unit was used for ceremonial public duties in the capital. The regiment disbanded in June 1921 and shortly after was revived as Kommando der Wachtruppe (lit. Headquarters Guard Troop).
The Wachtruppe comprised seven companies, each drawn from one of the seven active army divisions. Each company served for three months before returning to their parent division. In this way, the Wachtruppe represented the whole Reichswehr.
The Kommando was based at Moabit Barracks, and every Monday, Wednesday, Friday and Saturday, performed a modest changing of the guard ceremony for the public. On each Sunday, Tuesday and Thursday, the entire Wachtruppe, accompanied by the regimental band, marched from the barracks through the Brandenburg Gate and to the Berlin War Memorial, providing a greater spectacle for public view.
In 1934, the unit was renamed Wachtruppe Berlin and in 1936, a headquarters and administration company were added. In June 1937, the unit was again renamed Wach Regiment Berlin. Postings were now done by individuals, not entire companies, and each man served six-month tours of duty. The unit provided escorts and Guards of Honour for State Visits, Conferences and even the Olympic Games.
In 1939, the unit was reorganized as the Infantry Regiment Großdeutschland. While equipped as a field unit, the regiment also maintained a public duties detachment in the capital. The ceremonial guard was pressed into service during the July bomb plot in 1944 and helped round up conspirators in the capital.
Like the British Brigade of Guards at that time, the Großdeutschland maintained a strict height requirement.
United Kingdom 
Three infantry battalions of the British army are currently tasked with the provision of Public Duties. Two of these are from the Foot Guards of the Household Division, and one (since 1996) is a line infantry battalion. The former are normally based at Wellington Barracks in central London, within a short distance of Buckingham Palace, and at Victoria Barracks in Windsor Castle, while the latter is at the Cavalry Barracks, Hounslow. Permanent Public Duties companies of the Foot Guards also supplement these men.
Apart from providing the Queen's Guard at Buckingham Palace and St James's Palace, and the Tower of London Guard, the Public Duties battalions occasionally also provide the Windsor Castle Guard, which is otherwise provided by the battalion based at Windsor. From 1783 to 1973, the Guards provided a nightly detachment for guard duty at the Bank of England.
Public duties are also carried out in Edinburgh, although not as frequently as London. Prior to 2002, sentries were permanently stationed at the entrance to Edinburgh Castle, but these were withdrawn due to cost-cutting measures. Today, sentries are posted during the evenings between 6 pm and 9 am, and throughout the week that HM The Queen spends in Edinburgh at both the castle and the Palace of Holyroodhouse. Sentries are also posted at the castle during the month of the Edinburgh Military Tattoo prior to each performance, with the regiment forming a guard of honour at the end of each performance.
Unlike in London, there is no permanently based foot guards battalion stationed in Edinburgh, so public duties are performed by one of the resident line infantry/rifles battalions. However, as part of the Army 2020 plan, one of the battalions of the Royal Regiment of Scotland will be reduced to a single incremental company to be based permanently in Scotland for public duties.
Public duties are performed in Ottawa, the capital of Canada. The primary ceremonial duties involve mounting guard at the Canadian Parliament and at Rideau Hall, the official residence of the Governor General. These are performed primarily by the two Canadian regiments of foot guards (the Governor General's Foot Guards/Ottawa, and the Canadian Grenadier Guards/Montreal), detachments of which are formed into the Ceremonial Guard. However, as in London, it is possible that any Canadian regiment could serve in this capacity on authority of the Chief of Defence Staff. The guard at Parliament Hill and Rideau Hall are mounted daily from early June until late August, with the first parade usually on the Friday before Canada Day. The Governor General's Foot Guards, a Canadian Primary Reserve Unit, have often been called upon to perform additional public duties in Ottawa since their inception in 1872. Recently, the Ceremonial Guard has also been tasked to mount sentries on the Cenotaph, at Elgin and Wellington St.
United States 
Washington, D.C. 
Probably the best-known U.S. military unit to regularly engage in public duties is the 3rd U.S. Infantry Regiment ("The Old Guard") of the U.S. Army. Since April 6, 1948, the regiment is tasked with perpetually guarding the Tomb of the Unknowns at Arlington National Cemetery. The regiment also regularly takes part in White House ceremonies, including at state visits.
The other U.S. military services have their own ceremonial units.
- Spaeter, Helmuth History of the Panzerkorps Grossdeutschland (J.J. Fedorowicz Publishing)