Until this point in time he could tack the following successes to his flag:

Data from Historisches Marinearchiv:

https://historisches-marinearchiv.de/projekte/s_boote/beschreibung.php

During the nights April 23rd/24th and April 24th/25th 1943 the boats fired torpedoes against the landing piers at Cape Myšako and fought with Sovjet gunboats.

With exception of some few nights the boats performed advances against the Caucasian coast during each night until Aptil 30th 1943. 

On May 1st 1943 "S 47" transitted to Constanta for motoroverhaul while the 1. SFltl with "S 49", "S 51", and "S 102" to Kertsch (Kerč), in order to carry out reconnaissance from there to the Temrjuk-bight in the Azov Sea during the night May 1sr/2nd 1943 together with "R 35" und "R 163".

From the night May 3rd/4rh 1943 until the end of the first half year again reconnaissance operatins were performed to the Caucasian coast - mostly without any special events.

On May 13th 1943 "S 42 (Kptlt. Siems), "S 45" (Oblt.z.S. Günther Lutherer), and "S 46" (Lt.z.S. Günther Weisheit) arrived at Constanta as further reinforcements for the 1. SFltl.

On May 19th 1943 "S 51" transitted from Iwan Baba to Contanta for motoroverhaul.

In the morning of the May 20th 1943 after a sortie of the 1. SFltl with "S 26", "S 49", "S 52", and "S 72" against the Soviet supply trafic at the Caucasian coast, during which "S 72" sank a lighter (600 BRT), the boats on their way home were attacked again and again by Sovjet aircraft. "S 49" got plenty of hits above and below the waterline, two engines fell out, on "S 72" hull, auxiliary engines, and the fueltanks were damaged. Both boats had to be reported aKB. 

Soviet Ground Attack Aircraft attack with Aircraft Weapon - Picture: Archives Förderverein

On May 22nd 1943 "S 28" and "S 47" returned to Iwan Baba from motoroverhaul at Constanta.

Since May 23rd 1943 Kptlt. Büchting was commanding the flotilla replacing Korv.Kapt. Christiansen until he officially took command of the flotilla on September 9th 1943.

During the night May 25th/26th 1943 "S 40", "S 42", "S 45", and "S 46" reconnoitred off the bight of Temrjuk in the Azov Sea and entered Kerč in the morning. The same in the following night. 

The same night "S 51" transitted from Constanta to Sewastopol and May 28th/29th 1943 from Sewastopol to Iwan Baba.

The IV. MAS Flotilla of the Regia Marina (italian navy) stationed at Feodosija changed owner on May 20th 1943 and came as 11. S-Fltl into German ownership with seven boats of type MAS 500. Flotilla-commander became Kptlt. Hans-Jürgen Meyer. The flotilla was divided up into two groups as followes:

1. Group

2. Group

MAS 526 - Picture: Regia Marina

They constituted only a unimportant reinforcement of the S-boat-force in the Black Sea, since the main engines were very disruptive and the boats had a very poor sea-worthiness. At the transfer of the boats "S 506" was damaged by a bomb hit.

On May 21sr and 22nd 1943 the two ready for sea boats executed singleboats training. On May 24th 1943 all boats besides of "S 506" performed flok- and grouptraining. When entering harbour "S 507" run into a wreck and was damaged much. She had to be taken on a slip-way at Feodosija on May 25th 1943.

On May 25th and 26th 1943 the weather kept boats of the 11. SFltl in harbour.

On May 27th 1943 "S 501" and "S 505" performed pair-training and on 28.05.1943 they passed group-training, "S 502" was unserviceable because of a wire caught in the propellers, "S 501" had reduced revolutions of the engines. On May 29th 1943"S 503", "S 504", and "S 505" performed group-training.

On May 30th 1943  "S 40", "S 42", "S 45", and "S 46" of the 1. SFltl entered Iwan Baba. On paper the 1. SFltl had 12 boats available on  June 1st 1943:

The 1. SFltl with "S 26", "S 28", "S 47", and "S 52" laid mines in the Strait of Kerč on June 1st 1943. 

During the nights June 5th/6th and 8th/9th 1943 "S 501", "S 503", and "S 505" of the 11. SFltl had an anti-submarine operation southeast of the Crimea, so had "S 501" and "S 505" on June 10th 1943.

On June 7th 1943 occured a bomb raid against the harbour of Feodosija, "S 507" was damaged by fragments.

On 1June 11th 1943 "S 501", "S 504," and "S 505" carried out an inspection voyage for Admiral Black Sea (Admiral Schwarzes Meer[ (ASM]).

During a picket operation of "S 501", "S 504", and "S 505" during the night June 12th/13th 1943 the boats were hunted by Soviet S-boats but could escape without damages.

During the following night the 11. SFltl with "S 501" , "S 504", and "S 505" again formed a picket line, "S 505" had to give up prematurely because of engine failure.

On June 18th 1943 "S 502", "S 504", and "S 505" sailed to Iwan Baba and back to transport personnel to the inspection by F.d.S., "S 505 " had to return early because of engine failure.

The few available boats carried out picket operations and resultless anti-submarine warfare actions until end of the month.

During almost every night until the end of the month June the 1. SFltl performed resultless sorties or reconnaissance operations off the Caucasian coast with four to seven boats.

Also the second half of the year 1943 started for the 1. SFltl with reconnaissance operations and sorties against the Caucasian coast. 

The 11. SFltl in July 1943 carried out reconnaissance operations against the Caucasian coast and fought against the own delicate engines.

During the night  July 1sr/2nd 1943 "S 40", "S 46", "S 51", and "S 102" carried out reconnaissance in the Azov Sea, while "S 28", "S 42", and "S 47" advanced against the Soviet supply trafic off the Caucasian coast.

During the night July 3rd/4th 1943 an advance against Soviet suply trafic with boats "S 28", "S 46", "S 47", and "S 102" had to be broken off because of bad weather. 

During the night July 5th/6th 1943 during a further advance with "S 28", "S 40", "S 47", and S 51" three lighters were sunk by "S 28".

 During the night July 7th/8th 1943 an attack of the 1. SFltl with "S 28", "S 40", "S 42", "S 46", "S 47", "S 72", and "S 102" in three groups against a reported convoy came too late. "S 40" collided with "R 33" and was damaged seriously. Since both avarists could only proceed at a speed of seven knots, "S 102" and "S 28" sailed on ahead and "S 42" and "S 45" escorted the avarists. "S 102" (Lt.z.S. Lutherer) hit a mine in the Straits of Kerč and had  to be given up after an hour in spite of an attempt of "S 28" to tow her. Eight men of the crew had been killed. 

 "S 40" transitted on July 26th 1943 together with "S 42" and "S 47" from Iwan Baba to Constanta and was towed from there to Linz, were it came into the shipyard on September 15th 1943.

The remaining boats performed reconnaissance operations and advances against the Caucasian coast.

For the time from July 16th until August 15th 1943 there is a lack of data, since no KTB is available.

Impressions of the Wreck of "S 102" near Kerč - Pictures: A. Makarow

Sailors' Graves at Iwan Baba - Picture: Archives P. v. Glasenapp

 On July 26th 1943 "S 51" and "S 26" reported the sinking of a coastal freighter and a barge off Cape Myšako, in fact they sank the Floating Battery No. 627.

During the operations in July 1943 off Tuapse and Novorossijsk the boats of the 2. SFltl sank three coasters, one motorgunboat and one motortorpedoboat.

On September 9th 1943 the Red Army landed in the city of Novorossijsk. Six days later the town had to be evacuated. 

0n September 9th 1943 Kptlt. Büchting took over command of the flotilla from Korv.Kpt. Christiansen.

 On September 11th 1943 Soviet ground attack aircraft attacked the boats of the 1. SFltl returning home. They dived unimpressed by the defence fire down to 10 m and fired with aircraft weapon. On "S 46" (Oblt.z.S. Weisheit) all engines became unserviceable, the torpedo in the port tube exploded and tore off the forecastle all the way to the bridge. In spite of the continued attacks "S 49" went alongside and took over the partly seriously wounded crew and two killed in action. The boat was scutled with a torpedo.

Soviet Ground Attack Aircraft firing at the Boats - Picture: Archives Förderverein

Bad weather and bright moonlight prevented or hindered the operations of the S-boats during the next nights. The 1. and the 11. SFltl conducted picket operations again since the army feared a landing in their rear. The boats carried out search stripes south of  Anapa until the town was evacuated on September 21st 1943 in the frame of withdrawing movements. 

"S 47" coming alongside in the Black Sea still with the old bridgehouse - Picture: Archives Jürgens

During the night September 27th/28th 1943 four boats of the 1. SFltl fired at ships at the mole of Anapa. To minesweepers, one motorlaunch, and one patrolboat were hit. The mole was damaged.

During the night September 38th/29th 1943 the same boats sortied to Anapa again. No enemy vehicles were sighted.

The 11. SFltl was because of permanent engine problems and lack of spareparts dissolved on September 30th 1943. The personnel becoming free was withdrawn in favour of the 24. SFltl which was to be formed in the Aegean Sea with the conquered Italian boats. "S 501", "S 506", and "S 507" were subordinated the 1. SFltl but decommissioned already on October 5th 1943 at Feodosija.  The aKB boats transitted to Nikolaev, there "S 505" was decommissioned. The other three boats were going to Linz for repairs, their wherabouts is not cleared.

Mid  November"S 26", "S 28", "S 42", "S 45", "S 47", "S 49", "S 51", and "S 72"were ready for action at Iwan Baba. "S 40" was still in the shipyard as result of her collision with "R 33", the announced six boats as reinforcement from home were long in coming. "S 131", "S 149", and "S 148" were only launched in October or November. They became ready for action only on April 1st 1945.

"S 40" had been launched already on November 20th 1943 at Linz, however, during refuelling a fire had developped in the engineroom and the boat had to be repaired there. The transit to Constanta in tow was carried out from December 1st to 10th 1943. At Constanta the boat got a kalotte and was therefore aKB until February 15th 1944. 

"S 28" in the Black Sea off Iwan Baba - Picture: Archives F.K. Künzel

On November 13th 1943 KKpt. Christiansen was awarded the oak leaves to the knight's cross (Eichenlaub zum Ritterkreuz).

KKpt. Georg Stuhr Cristiansen - Picture: Archives Behrens

During the second half of November the operations were directed against the Soviet bridge-head at Kerč. On November 17th 1943 it came to a fight with the Soviet S-boats "TK-76", "TK-86", and "TK-104". "TK-76" did not return to her harbour, the other two boats were damaged. On November 21st 1943 the flotilla shot two landing-vessels on fire and pushed eight others off to the east so that they could not land their cargo.

On November 30th 1943 "S 28", "S 45", and "S 49" transitted to Constanta for a shipyard period. "S 28" got a Kalotte and a 40mm gun and returned not earlier than Match 3rd 1944 under the new commanding officer (StObStrm Peter Neumeier, from March 1st 1944 Lt.z.S. (KRO) to Iwan Baba.

On DEcember 12th 1943 Oblt.z.S. Künzel, commanding officer of "S 28", was awarded the knight' cross (Ritterkreuz) for more than 200 sorties.

Oblt.z.S. Karl Friedrich Künzel - Picture: Archives Künzel