by Matto Mildenberger and Stephen Peters
Problem: Arbor Day Town/​Pi Day Town

Solvers are initially presented with 10 enumerated clues. Each clue is written in the first person and describes the accomplishments of a US military officer who was later honored by having a naval ship named after them. Each clue resolves to the ship named after the officer. (Each ship name is preceded by USS, which is indicated by the fact that every single ship begins with a three letter ??? word.) This dataset is also clued by the flavor (“things that were commemorating sailors”).

The ships are presented in alphabetical order. They are:

[Richard Swan] Baron: I was killed in WWII during the bombing of Cebu City. And I’d just received the Navy Cross for risking my life to recover classified documents during the bombings of Cavite!
[Godfrey de Courcelles] Chevalier: I was the first naval officer to land on the first American aircraft carrier! I also commanded the naval air station at Dunkirk, but died at 33 from injuries suffered in a Virginia plane crash after the war. I hear they named a Medford theater after me.
Eugene A. Greene: After enlisting in the US military in 1941, I joined an airborne squadron during World War II. I died during the Battle of Midway in 1942 when I heroically attacked a Japanese carrier amidst heavy fire, giving me my posthumous Navy Cross. Unlike the other people like me, I was the youngest at the time of my death, and I was born in Smithtown, New York.
[John T.] Eversole: After graduating from the US Naval Academy in 1938, I joined an airborne squadron during World War II. I died during the Battle of Midway in 1942 when I heroically attacked a Japanese fleet amidst heavy fire, giving me my posthumous Navy Cross. Unlike the other people like me, I was the oldest at the time of my death, and I was born in Pocatello, Idaho.
[Lofton] Henderson: After graduating from the US Naval Academy in 1926, I served around the world, including in China and the Caribbean. I led a force of dive bombers in an attack on the Japanese aircraft carrier Hiryū but my plane caught fire on final approach. I received a posthumous Navy Cross.
Henry W. Tucker: I served in the Pacific as a pharmacist’s mate. A case of mistaken identity led the Japanese to all-out attack my oiler as if it were an aircraft carrier. My captain ordered the crew to prepare to abandon ship, but in the confusion many of my mates believed the abandon-ship order had already been given and jumped off the ship prematurely. Ignoring my own safety I swam around treating burned and wounded soldiers, helping them to life rafts, while refusing a place on these rafts myself. I received a posthumous Navy Cross.
[Randolph Mitchell] Holder: I joined an airborne squadron during World War II. I died during the Battle of Midway in 1942 when I heroically attacked a Japanese fleet amidst heavy fire, giving me my posthumous Navy Cross. Unlike the other people like me, my death was declared one day later, and I was born in Jackson, Mississippi.
James E Kyes: Back when I was a WWII naval commander, three torpedoes hit my ship. The crew began to evacuate the sinking vessel. But then I spied a kitchen mess boy without a functioning life jacket. I gave him my life jacket instead and, without any protection, I calmly met my end in the cold waters of the Atlantic Ocean.
[Carl Theodore] Vogelgesang: Before I became a rear admiral and won my Navy Cross, I was the first naval flag officer from California. I also learned Portuguese in just six weeks after President Harding sent me to Brazil to promote friendly relations between our two countries.
[Morgan] Wesson: I was born in Longmeadow, Massachusetts and joined the navy in 1941. I was killed in the Battle of the Solomon Islands, and posthumously received a purple heart. My mother Eleanor was instrumental in having me honored after my death.

Each of these ships has something in common: they were decommissioned and sold to another country’s navy. These new navies renamed the ships.

Every ship’s US name can be transformed into the foreign navies’ new name for that ship in five steps. Solvers are given 5 lists of string transformations, with each list presented alphabetically. Solvers must use one transformation from each list in order to transform each ship’s name from old (US) to new (foreign). In doing so, they will discover that the resulting name also includes an extra letter.

These transformation sequences are as follows (with the final extra letter bolded):

USS BARONDivide the string in two equal halves, and switch their order.
ARONUSSBFind a Greek letter name, and replace the first letter in that name with its last letter. [NU → UU]
AROUUSSBReplace the double consonant that follows a double vowel with a word for a floor covering. [SS → RUG]
AROUURUGBOne vowel occurs three times in a four-letter substring. Insert a fourth copy of that vowel before the last letter of the full string.
AROUURUGUBThe last letter of the string is the first letter of a three-letter word for a body of water. Replace it with the other two letters in that word. [B → AY]
A ROU URUGUAY(Navy: Uruguay)
USS CHEVALIERReplace an acronym for an Asian airline with the IATA code for Kiunga Airport. [EVA → UNG]
USSCHUNGLIERThe first two and last two letters together spell a word; remove them.
SCHUNGLIReplace the only occurrence of a symbol for a New York subway line you can take to Canarsie with the Polish word for “beech”. [L → BUK]
SCHUNGBUKIPrepend a common expression that likely emerged as an abbreviation of a humorous spelling of the phrase ‘all correct’. [OK] The string will now contain an abbreviation for the complex that launched the Apollo rockets. [KSC]
OKSCHUNGBUKIThe string contains a four letter word which is often followed by another four-letter word in legal parlance. Prepend the third letter of that other word to the full string. [HUNG (juRy)]
ROKS CHUNG BUK I(Navy: South Korea)
USS EUGENE A GREENEDrop all instances of the vowel that appears six times.
USSUGNAGRNReplace a word meaning to pester with a word meaning place of worship. [NAG → CHURCH]
USSUGCHURCHRNReplace all Rs with double Rs, then remove the last three letters. The string will now contain the same number of Rs it had before doubling.
USSUGCHURRCHRemove the fourth and fifth letters, which should be the last two letters of a word meaning a container for coffee. [mUG] Sandwich the second C between the abbreviation for a film studio co-founded by Charlie Chaplin. [UA]
USSCHURRUCAHThe sixth and seventh letters are the second half of a word for a player on a particular NBA team; replace the string’s first two letters with the first half of that word. [SPur]
USS EVERSOLEReplace the word for a type of fish with the name of one of the five free cities located in the Chondath region of the Vilhon Reach. [SOLE → RETH]
USSEVERRETHOf the two sets of double letters, replace the double letter closer to the end of the alphabet with the two-letter country code for Brazzaville’s country. [SS → CG]
UCGEVERRETHReplace a word that precedes “after” in a common phrase with one that can follow “Enola”. [EVER → GAY]
UCGGAYRETHRemove the leftmost appearance of a metallic element symbol. [U (uranium)]
CGGAYRETHAdd a copy of the second to last letter to the beginning of the string.
TCG GAYRET H(Navy: Turkey)
USS HENDERSONReplace the final word from many old movies with the postal abbreviation for Rhode Island. [END → RI]
USSHRIERSONAdd a word for a harbor boat before an abbreviation for a baseball scoring play. [TUG, HR]
USSTUGHRIERSONRemove a concluding preposition. [ON]
USSTUGHRIERSReplace a long-running TV series with a symbol for a unit of volume. [ER → L]
USSTUGHRILSChange the first two letters so that the string’s first five letters are an anagram for what an NFL player perhaps does on fourth down [PUNTS], and the second through fifth letters are an anagram for a Streisand movie. [NUTS]
PNS TUGHRIL S(Navy: Pakistan)
USS HENRY W TUCKERReplace the name of an ill-fated US car company from the late 1940s with the word for a raised platform. [TUCKER → DAIS]
USSHENRYWDAISReplace a word for a female bird with a two-letter nickname for a parent. [HEN → MA]
USSMARYWDAISReverse the order of any side-by-side vowels that occur in alphabetical order.
USSMARYWDIASReplace a chatroom response to “ty” with a word describing a paramecium’s propellers. [YW → CILIA]
USSMARCILIADIASRemove two of the three letters at the beginning of the string, without removing two of the same letter. Then, change one letter in a 1998 top 20 song to make a language spoken in Rourkela. [ADIA → ODIA]
USS HOLDERTurn a five-letter adjective describing comparative age into a five-letter adjective describing reliable support. Then, prepend the letter P. [OLDER → LOYAL]
PUSSHLOYALAppend a word for a fortune-telling deck; the string will now contain the name of a famous conference. [yalTAROT] Then, prepend a modern three-letter slang term for a boyfriend or girlfriend. [BAE]
BAEPUSSHLOYALTAROTFind the name of a boot-wearing fairytale character. [PUSS] Then, replace the last two letters of the name with the first two initials of a Cambridge poet who avoids capitals. [EE]
BAEPUEEHLOYALTAROTReplace the first name of a UN Secretary General (in front of a pair of vowels) with a term for a doctor in training. [U → RESIDENT]
BAEPRESIDENTEEHLOYALTAROTConvert the letter five places from the end of the string to its opposite. [T → F] Then, remove the letter immediately following a double vowel.
USS JAMES E KYESFind the three-letter abbreviation for a Scandinavian currency, and drop the last two letters of it. [SEK → S]
USSJAMESYESChange the second occurrence of the top-level domain for Spain into the top-level domain for India. [ES → IN]
USSJAMESYINReplace the three-letter word at the end with its opposite. [YIN → YANG]
USSJAMESYANGReplace an Iowa college town with the French name for an Aidi, Akita, or Airedale. [AMES → CHIEN]
USSJCHIENYANGReplace a multi-letter pronoun with the word for a legendary bird of prey. [US → ROC]
USS VOGELGESANGReplace the word for bird in a European language with the name of Guatemala’s currency. [VOGEL → QUETZAL]
USS QUETZALGESANGOne letter appears twice in a row. Replace this double letter with one instance of the letter preceding it in the alphabet.
UR QUETZAL GESANGReplace the past tense of a word meaning “produce sounds with musical intonation” with a word for an article of clothing. [SANG → COAT]
UR QUETZALGECOATRemove the letters that are a brand of home appliance. [GE]
UR QUETZAL COATChange an R in one of the first two positions of the string into a three-letter word for a body part. [R → ARM] Then, add an L to the end of your string.
USS WESSONReplace the first name of a filmmaking auteur who has has been nominated for three screenplay Oscars with the first name of a US Senator who is the son of a former Congressman from another state. [WES → RAND]
USSRANDSONReplace a word for a child with the capital of Italy. [SON → ROME]
USSRANDROMEAppend the word for Hugo Ball’s art movement to the full string. [DADA]
USSRANDROMEDADARemove the last letter in a four-letter string that is comprised of two repeated two-letter strings.
USSRANDROMEDADRemove the abbreviation for a Cold War country. [USSR]
ANDROMEDA D(Navy: Italy)

Solvers will notice that each ship transforms into a vessel for a different foreign navy.

US ShipForeign shipNavyExtra
USS James E. KyesROCS Chien YangTaiwanJ
USS WessonAndromedaItalyD
USS HendersonPNS TughrilPakistanS
USS EversoleTCG GayretTurkeyH
USS BaronROU UruquayUruguayA
USS HolderBAE Presidente Eloy AlfaroEcuadorT
USS Henry W TuckerMarcilio DiasBrazilS
USS VogelgesangARM QuetzalcoatlMexicoU
USS Eugene A GreeneESPS ChurrucaSpainH
USS ChevalierROKS Chung BukSouth KoreaI

Each navy is represented by one of the ten flags at the bottom of the puzzle. Ordering the extra letters by this flag order gives the phrase JDS HATSUHI. Solvers must now reverse this Japanese ship’s transformation. The JDS Hatsuhi was originally called the USS ATHERTON, which is the puzzle answer.