Peoshan was instructed to bury F/O Olsen temporarily at Maliping and his personal effects were to be sent to the 1337th AAF BU ASAP. On 7 April 1945, the 1337th AAF BU reported that the remains of F/O Olsen, 1stLt Martin were located and buried in temporary graves at the airfield at Wamati (map coord. 26º 06’ North & 98º 54’ East) by Missionary Peterson. Mr. Guy C. Martin of Martelle, Iowa, wrote the Washington, D.C. Casualty Affairs office asking for further information about his son, 1stLt Martin, and the accident which took his life. The 1337th AAF BU replied to Washington, D.C., that Base Commander Lt.Col. Cassady sent two letters to Mr. Martin about the accident. The Base Chaplain sent a letter as well. John P. Olsen is remembered on the memorial wall of the missing in the Manila American Cemetery & Memorial, Philippines.
His brother, Robert F. Olsen, born 28 May 1924, served in the U.S. Marine Corps, a Corporal, was killed in action on the island of Peleliu, Palau, in the South Pacific, on 24 September 1944. He was buried in the Forest Park Cemetery, Houston, Texas. The Battle of Peleliu was fought during the Mariana and Palau Campaign from September to November 1944. On the second day, the 5th Marines moved to capture the airfield and push toward the eastern shore. They ran across the airfield, enduring heavy artillery fire from the highlands to the north, suffering heavy casualties in the process. After capturing the airfield, they rapidly advanced to the eastern end of Peleliu, leaving the island's southern defenders to be destroyed by the 7th Marines. This area was hotly contested by the Japanese, who still occupied numerous pillboxes. Heat indices were around 115 °F (46 °C), and the Marines soon suffered high casualties from heat exhaustion. Further complicating the situation, the Marines' water was distributed in empty oil drums, contaminating the water with the oil residue. Still, by the eighth day the 5th and 7th Marines had accomplished their objectives, holding the airfield and the southern portion of the island, although the airfield remained under threat of sustained Japanese fire from the heights of Umurbrogol Mountain until the end of the battle. American forces put the airfield to use on the third day. L-2 Grasshoppers from VMO-1 began aerial spotting missions for Marine artillery and naval gunfire support. On September 26 (D+11), Marine F4U Corsairs from VMF-114 landed on the airstrip. The Corsairs began dive-bombing missions across Peleliu, firing rockets into open cave entrances for the infantrymen, and dropping napalm; it was only the second time the latter weapon had been used in the Pacific. Napalm proved useful, burning away the vegetation hiding spider holes and usually killing their occupants. The time from liftoff to the target area for the Corsairs based on Peleliu Airfield was very short, sometimes only 10 to 15 seconds. Consequently, there was almost no time for pilots to raise their aircraft undercarriage; most pilots did not bother and left them down during the air strike. After the air strike was completed and the payload dropped, the Corsair simply turned back into the landing pattern again. The 5th Marines—after having secured the airfield—were sent to capture Ngesebus Island, just north of Peleliu. Ngesebus was occupied by many Japanese artillery positions and was the site of an airfield still under construction. The tiny island was connected to Peleliu by a small causeway, but 5th Marines commander Harris opted instead to make a shore-to-shore amphibious landing, predicting the causeway to be an obvious target for the island's defenders. Harris coordinated a pre-landing bombardment of the island on September 28, carried out by Army 155 mm (6.1 in) guns, naval guns, howitzers from the 11th Marines, strafing runs from VMF-114's Corsairs, and 75 mm (2.95 in) fire from the approaching LVTs. Unlike the Navy's bombardment of Peleliu, Harris' assault on Ngesebus successfully killed most of the Japanese defenders. The Marines still faced opposition in the ridges and caves, but the island fell quickly, with relatively light casualties for the 5th Marines. They had suffered 15 killed and 33 wounded and inflicted 470 casualties on the Japanese. The battle was controversial in the United States due to the island's lack of strategic value and the high casualty rate. The defenders lacked the means to interfere with potential US operations in the Philippines, and the airfield captured on Peleliu never played a key role in subsequent operations. The high casualty rate exceeded all other amphibious operations during the Pacific War.