BRP Rajah Humabon ( PF - 11 ) The BRP " Rajah Humabon " ( PF - 11 ) is a frigate of the Philippine Navy , and is the last World War II - era destroyer escort / frigate active in its fleet and is one of the oldest active warships in the world . She is one of three ex - USN s that served the Philippine Navy , the others being BRP " Datu Sikatuna " ( PF - 5 / PS - 77 ) and BRP " Datu Kalantiaw " ( PS - 76 ) . History . United States Navy . Commissioned in the US Navy as the in 1943 , she was mostly assigned at the Atlantic theatre doing patrols and anti - submarine missions . She was credited of having destroyed a German U - boat , the " U - 853 " off the coast of Rhode Island , on 9 May 1945 . She served in the Pacific theatre in the middle of 1945 until she was decommissioned and placed in reserve on 10 December 1945 . For her service during World War II , she was awarded with one battle star . Japan Maritime Self - Defense Force . She was transferred to the Japanese government as JDS " Hatsuhi " ( DE - 263 ) on 14 June 1955 . Together with her sistership JDS " Asahi " ( DE - 262 ) , they became one of the first warships of the newly organized Japan Maritime Self - Defense Force . As newer ships became available to the JMSDF , both ships were decommissioned and returned to the US Navy on June 1975 . Philippine Navy . Remained laid - up in Japan , she was transferred to the Philippine government in 13 September 1976 and was sold as Excess Defense Article on 23 December 1978 . As a Philippine Navy ship , she was named RPS " Rajah Humabon " ( PS - 78 ) , and was towed to South Korea for an extensive refit and modernization in 1979 . During this period South Korea also turned over 2 of their own ex - USN " Cannon " class ships to the US Navy in 1977 , namely the " Kyong Ki " ( DE - 71 ) / and " Kang Won " ( DE - 72 ) / . These were also turned - over by the US to the Philippine government , which were later on cannibalized for use as parts hulk to upgrade and repair the " Rajah Humabon " and her sistership " Datu Sikatuna " , and provide both ships with additional guns and improved machinery . With these upgrades , she was formally commissioned to the Philippine Navy on 27 February 1980 , and formed the backbone of the Philippine Fleet together with 2 of her sister ships and other ex - US Navy destroyer escorts . She was renamed and reclassified as BRP " Rajah Humabon " ( PF - 6 ) effective 23 June 1980 , now using the " BRP " ship prefix in lieu of " RPS " and following a new standard classifying it as a " Frigate " , and served until 1993 when she was retired . But due to pressing needs , she was later called back into service in 1995 after being overhauled at the Cavite Naval Dockyard by Hatch & Kirk Inc . , and was formally recommissioned in January 1996 as BRP " Rajah Humabon " ( PF - 11 ) with a new hull number . Another minor refit between 1995 and 1996 saw changes in the ship ' s weapons , sensors and engine systems . Her anti - submarine weapons and equipment were removed due to lack of spare parts . This includes the EDO SQS - 17B hull - mounted sonar , a Mk . 9 depth charge rack , six Mk . 6 depth charge projects aft and a Hedgehog Mk . 10 anti - submarine projectors forward , as well as Mk . 38 anti - submarine torpedoes in two triple tube amidships . This totally removed her anti - submarine warfare capabilities , which was outdated on modern conditions . But it was reported in 2005 that her fore Hedgehog ASW is still operational , together with her 8 K - gun Mk6 depth charge projectors and SQS - 17B sonar , although recent photos does not show the depth charge projectors on its usual location . She had been experiencing hull problems but was repaired with the assistance of the US Navy crew of during CARAT 2002 dive training operations held in Manila Bay . Additional electronic upgrades were made , including the installation of a Furuno Satellite Communication system and a mast - mounted FLIR package . Present Status . Her current classification is Patrol Frigate . As recent as May 2010 she was part of the Philippine Navy contingent for the RP - US Balikatan 2010 exercises , and continue to operate from the Philippine Navy ' s main naval base in Cavite and visits the Navy Headquarters in Manila . She is currently assigned to the Patrol Force of the Philippine Fleet . Technical details . Armaments . Although fairly well - armed , most of her weapon systems are manually operated and are of World War II origin . The three Mk . 22 3 " / 50 caliber gun s , the ship ' s primary weapons , have a range of up to and are also capable of being used as limited anti - aircraft weapon . The guns were directed by a Mk . 52 gun fire control system with a Mk . 41 rangefinder , but this appears to be non - operational . She also carries a total of three twin Mk . 1 Bofors L / 60 40 mm anti - aircraft guns directed individually by Mk . 51 gun fire control system , six Mk . 4 20 mm Oerlikon cannons , and four M2 Browning 50 caliber machine guns . All anti - submarine weapons were removed as of 1996 . Machinery . The ship is powered by two EMD 16 - 645E7 turbo - blown diesel engines with a combined power of around driving two propellers . The main engines can propel the 1 , 620 ton ( full load ) ship at a maximum speed of around . It has a range of at a speed of . It replaced the original four EMD 16 - 278A diesel engines during the ship ' s overhaul in 1996 . Electronics . The ship is equipped with a Raytheon AN / SPS - 64 ( V ) 11 short range surface search and navigation radar and a Furuno navigation radar , replacing the SPS - 5 surface search radar and the RCA / GE Mk . 26 navigation radar . Previously equipped with an EDO AN / SQS - 17B hull - mounted sonar , it is said to be deleted in 1996 due to lack of spare parts and obsolescence although it was reported to be still present in 2004 . Notable Operations . Deployments . On 17 June 2011 the " Rajah Humabon " was sent for patrols around the Scarborough Shoal after China announced that its biggest maritime patrol vessel , the " Haixun 31 " , will be sent to the area on its way to Singapore . International . On 2 February 2000 , the " Rajah Humabon " fired warning shots at two Chinese fishing boats near Scarborough Shoal . According to Navy chief Vice Admiral Luisito Fernandez , the " Rajah Humabon " was forced to fire warning shots to avert a collision with two Chinese fishing boats and only after the Chinese boats refused to respond to radio contact , loudspeaker , sirens , and flashing lights . On 22 June 2002 , " Rajah Humabon " together with BRP " Rizal " visited Shanghai , China for a goodwill visit . Exercises . The " Rajah Humabon " , together with BRP " Leopoldo Regis " ( PG - 847 ) , BRP " Dagupan City " ( LC - 551 ) , BRP " Artemio Ricarte " ( PS - 37 ) , , and were part of the naval component of the US - RP Balikatan 2009 bi - lateral exercises held on April 2009 . Again " Rajah Humabon " , together with BRP " Dagupan City " ( LC - 551 ) , and BRP " Apolinario Mabini " ( PS - 36 ) , USS " Essex " ( LHD - 2 ) , and USS " Denver " ( LPD - 9 ) were part of the naval phase of the US - RP Balikatan 2010 ( BK10 ) bi - lateral exercises held on March 2010 . On 14 to 16 August 2012 , the Naval Forces Northern Luzon ( NFNL ) conducted a small - scale Naval Exercise code - named SAGEX 02 - 12 at the waters of South China Sea . BRP " Rajah Humabon " together with BRP " Gregorio del Pilar " and BRP " Liberato Picar " participated under Naval Task Force ( NTF ) 11 . The exercise includes patrol , simulated tracking of targets and interdiction and capped by live firing exercises . " Rajah Humabon " , together with BRP " Gregorio del Pilar " participated in the sea phase exercises with the US Navy during the Balikatan 2013 from April 5 to 17 , 2013 .