Why was the C-pennant chosen as the flag of ships from Allied-occupied Germany?

The by order of the allies since 1945 by german ships to use flag is corresponding to the flag C of the signal-flag-alphabet. Behind this conceals the humiliating intention to let ride german ships on the oceans only with the letter C, standing for Capitulation. Costa Rica made an appeal against this practice, because it is self using such a flag as national flag. In this way they have the c-flag rectangular carved on the flying end. With the founding of the FRG and the GDR, this practice was eliminated.

"Germany will not be occupied for the purpose of liberation but as a defeated enemy nation."

US-american Directive of Occupation JCS 1067

• Ship flag: occupied Germany 1945–1949

Historical vexillologists do not know a definitive answer.

What is known is that the Allied Control Council Law No 39 from November 1946 made it mandatory to display such a c-pennant-like flag instead of a 'national flag', but not as a national flag (meaning also not at the usual position on masts etc). (Law 39 on page 166 PDF, German translation on WP: Erkennungsflagge für deutsche Handelsschiffe).

This was done as all German flags were ordered illegal as of May 1945, but in international waters a ship would still need this kind of identification. Absolutely no flags would mean in international law that a ship was stateless or engaged in piracy… From May 1945 onwards there were absolutely no German flags allowed.

(g) Administrative Affairs. Other measures refer to administrative matters requiring uniform regulation by a central agency, such as adopting standard time throughout Germany; arranging for a population census; and certain arrangements incidental on the occupation and its technical requirements.¹²⁰

^120: Law No. 39 of Nov. 12, 1946 on "Distinguishing Flag to be Worn by German and Ex-German Ships Operating Under Allied Control Authority," OG/CC, No. 12 at 226 (Nov. 30, 1946);
_{— Karl Loewenstein: "Law and The Legislative Process in Occupied Germany: I", The Yale Law Journal, Vol. 57, 724, 1948. (PDF)}

As the text of this law from 1946 makes explicit (in excerpt):

Article 1

1. In all cases, except as provided in Article III, every German or ex-German vessel operating under the allied Control Authority shall at all times wear the Allied Control Authority distinguishing flag which shall consist of Inter­national Flag "C" with a triangle cut from the fly, as shown in the Schedule hereto,
2. This flag […] and shall be treated as a distinguishing flag.

There is rife speculation as to whether the meaning of "C" was meant as a constant reminder of defeat as it would stand as an abbreviation for 'C'apitulation. Certainly, this was a 'popular' German interpretation for this derogatorily called "bathing pants flag", as even the German minister for transport Seebohm (Hans-Christoph, not the Nazi-admiral Hans!) alluded to this reading in 1951 when the first black-red-gold German national flag on ships was again allowed to be flown on ships:

Everyone knows the symbolic meaning associated with this flag.
_{— Seebohm when on board the first ship with the new flag, MS Messina, 23 February 1951. (quoted from Biegler)}

Other speculations are for example from Stödter who maintains that the letter C would also allude to prizes (meaning that it would be effective even long before the official capitulaion/surrender), as such would be the quasi-official collective status for German ships after 1945.

Biegler himself prefers – without better evidence – that it would be short for "Control", as in 'Control Council'. And that the colours present in that pennant would indeed match all 4 allies' national flags.

— Thilo Biegler: "Flaggenführung der Schiffe und Boote der Deutschen Kriegsmarine nach der Kapitulation 1945", Fahnen Flags Drapeaux (Proceedings of the 15^th ICV, Zurich, 1993. PDF)

At least the name of the flag is also mentioned prior to Law No 39 in Directive 33 (5), August 16th, 1946 "Limitations of the Characteristics of Ships Left at the Disposal of Germany", (PDF, PDF-p72/p60)) as the 'Allied Authority Control flag'.

However, these speculations do not have any direct evidence to support them, but also a few circumstantial data points that make them less plausible.

The first would be that for Japan, three different flags were ordered in much the same manner, but obviously different from the 'German' identification flag — and without any such readily interpretable letter meaning:

Two 'Japanese' flags meaning

• "E"/"I am altering my course to starboard."?
• "D"/"Keep clear of me; I am maneuvering with difficulty."?

The third then a modified "O" carrying "man overboard meaning" as a flag?

Why would the German version get such a 'special meaning' by intention but not the Japanese versions?

The next objection would be found in the timing. Already on May 7th 1945 German ships were ordered to display a black flag or a blue flag as a sign of surrender. Additionally, allied ships were ordered to also accept a white flag for the same purpose.

Then already on May 9th 1945 a provisional order went out that proscribed for German or ex-German ships to have the C-pennant. That order and the British practice to talk about "under allied control" and this pennant as literally the "control flag" might mean indeed that 'C'ontrol was an early meaning that for very simple and practical reasons then was solidified into Law No 39?

It might be added that in German flag alphabets it is also listed as

C – Charlie – Yes

and in regatta sports as

"change of course in the next section"

The British War Diary Summaries record this:

WDS, radio, 9.5 1945. .From ANCXF.

To All Flag Officers in Charge and Naval Officers in Charge.

(1) German war and merchant vessels required to operate in Allied interests with German crews are to fly at the peak International Code Flag C with a triangle cut from the fly thus transforming it into a burgee.

(2) If Allied naval officers are onboard the appropriate Allied Ensign is also to be worn superior.

(3) This arrangement is provisional.*
_{— quoted from Biegel}

A burgee is a distinguishing flag, regardless of its shape, of a recreational boating organization. In most cases, they have the shape of a pennant.

Notice that there are exceptions to 'all vessels': for the German Mine Sweeping Administration ships flew the signals "eight" and "Nanni", ten in addition the c-pennant and after its dissolution the CCG-flag. The successor organisation "Labor Unit B" were all German manned but flew the Star & Stripes… Ships on Soviet controlled territory a simple red 'worker's' flag. The order to hoist the "eight" signal-pennant was actually the last flag order of the Reishkriegsmarine issued by Dönitz on May 16 1945 (B.Nr .1.Skl. I i1212/45 PDF) (Incidentally, many captains also flew the signal "Q", without orders to do so. Which some say was a sign of protest over the 'no-flag' situation, as that should stand for Quatsch German für 'bullshit'. Nanni and Q were often confused.) It is remarkable that this last act of the Reichsregierung survived as a practical solution.

The German national version signal flag for "Nanny" or "Northpole" (and "8", "Q") looked like this:

And a comparison of 'flags' from Biegler:

The most important thing to observe might be the simple fact that neither Germany nor Japan were allowed to display any form of true national flag in that period. So my own speculation here is that any non-national flag would have made sense and fulfilled the purpose. Unless a British Navy internal for this rationale is dug up: the actual choice made in Law No 39 looks much like mere contingency based on prior art.

Some further reading elucidating a few of the legal implications as written by a German official: – Ministerialrat Heinz Kallus: "Gesetzgeberische Arbeiten der Bundesregierung auf dem Gebiet des öffentlichen Seerechts", Schriften des deutschen Vereins für Internationales Seerecht Reihe A: Berichte und Vorträge, Heft 3, Schiffahrts-Verlag Hansa. C. Schroedter & Co.: Hamburg, 1954. (PDF) And the maritime legal requirements and implications in WP: Flag state, as well as — John N. K. Mansell: "Flag State Responsibility: Historical Development and Contemporary Issues", Springer: Berlin Heidelberg, 2009.