While Vorpostenboote were able to engage and defeat light naval forces – such as small motor gun boats – they were not powerful enough to effectively combat destroyers or larger warships.
[4] At the outset of World War I, the Imperial German Navy lacked sufficient numbers of warships to perform auxiliary tasks like coastal patrol and convoy escort.
[9] Several Vorpostenboote were lost in the harsh winter of 1939, in part due to mines (called "drifters") which had been broken free from their moorings by the foul weather.
[12] During the invasions of Norway and Denmark in April 1940, Vorpostenboote continued their patrol duties and also escorted landing groups and tankers in ten convoys.
[14] Triton spotted the convoy on the afternoon of 10 April and sank both transport ships and Vorpostenboot Rau VI, resulting in the drowning of more than 900 German soldiers.
Compounding the problem, the complex and tangled jurisdictions of the German naval commands meant that almost all drifters and trawlers requisitioned at this time were sent to the Baltic Sea rather than being used to guard the Norwegian coast.
[16] There were a few minor windfalls for the stretched auxiliary forces, however, such as on 5 May when three British armed trawlers and a Norwegian torpedo boat ran aground in a German-controlled area to escape Luftwaffe bombers.
[17] Even though the invasion and occupation of Norway and Denmark consumed the bulk of available Vorpostenboote, patrols in the North Sea had to continue in order to keep U-boat routes safe and clear of mines.
During the entire period of the Battle of France, only a single Vorpostenboot was lost, when the Bayern struck a mine in the North Sea on 9 June.
In May, Antares fell victim to a mine and in June HMS Snapper ambushed a merchant convoy and sank Vorpostenboot Portland.
Initially, the command consisted of just four fishing ships and two Vorpostenboote, but it would eventually expand to 45 vessels spread between three Vp-flotillas and a minesweeper flotilla.
Poorly equipped and coordinated, the British bombers were unable to deal significant damage to convoys between Norway and Germany, partially because of effective protection offered by Vorpostenboote and Sperrbrecher escorts.
[23] However, these circumstances would shift in 1941 as Coastal Command received better aircraft, better intelligence, and the results of cracking German ciphers such as the Enigma codes.
The greater threat posed by aircraft led to a gradual increase in anti-aircraft armaments carried on Vorpostenboote as the war went on, ultimately resulting in them being dubbed "flak ships" by Allied aviators.
One convoy escorted by Vorpostenboote was attacked by a large Soviet force of four MTBs, various aircraft, the cruiser Kirov and its supporting destroyers.
Similar attempts to contest the Baltic were ultimately unsuccessful, but did serve to slow the German advance and prevent total control of the sea.
Following successful raids in the North Sea, the German capital ships Scharnhorst, Gneisenau, and Prinz Eugen ended up in port at Brest in Brittany for repairs and maintenance.
[29] The ships began to be harassed in port by British air attacks after Winston Churchill issued the Battle of the Atlantic directive, which sought to reduce the ability of Germany's surface fleet to raid commerce.
[32] At the same time, Adolf Hitler was convinced that the ships at Brest were required in the North Sea to contest an expected British invasion of Norway.
It was a Vorpostenboot, the John Mahn, which was attacked twice by groups of Lockheed Hudson bombers and several fighters, which riddled it with machine gun fire and struck it with two bombs, which ultimately caused the ship to sink.
Despite being escorted by multiple Vorpostenboote, these engagements often led to the sinking of minesweepers or merchant ships; in just the week of 13 March, five large steamers were sunk by MTBs.
The blockade runner , an Italian tanker SS Butterfly, was escorted by Vorpostenboote Carl J. Busch and Pilote XIII and two submarine chasers.
[46] At dawn, the battle expanded to the air, with two dozen Czech-piloted Spitfires strafing the German convoy before being engaged by Luftwaffe fighters.
When British ships and aircraft finally began to disengage at around six in the morning, one of the submarine chasers had been sunk, SS Butterfly was breaking up, and the Pilote had taken heavy casualties.
Surface operations in the Eastern Baltic had been almost completely stopped due to very poor sea state over a prolonged period of time coupled with Allied bombing of harbors and drydocks.
Two small German ships, whose identity has been attributed to Vorpostenboote Otto Bröhan and Friedrich Busse, steamed up the canal and counterattacked against the British forces now defending the bridge.
[54] Similar attacks continued throughout July, and in August what little forces the Kriegsmarine had remaining in western France were utterly destroyed in Operation Kinetic.
[55] The most devastating moments during the offensive occurred on 23 August during the defense of Brest, when seven Vorpostenboote of the 7th Vp-flotilla were ordered to break out from the harbor and head south to Lorient.
The ships set out in two groups, and the first (consisting of Memel, Marie Simone, and Michel François) were almost immediately detected by the light cruiser HMS Mauritius with two destroyers.
The group scattered: Memel and Michel François ran aground and Marie Simone was destroyed ship as it attempted to make for shore.