Iwo Jima translates as “Sulfur Island”, a name that gives some impression of its foreboding nature. Remote, volcanic and inhospitable at the best of times, on 19 February 1945, Iwo Jima presented US Marines with an especially unwelcoming landscape.

With American forces set to mount an amphibious attack on the island, Japan resolved to ensure that the engagement would be a long, bloody and dispiriting one, plotting to defend in depth and make the inhospitable terrain work to their advantage. Thirty-six days of World War Two’s most intense fighting lay ahead.

1. Iwo Jima is small

The island has an area of just eight square miles, making it all the more surprising that the battle lasted 36 days.

2. It is situated slap bang between Japan and the nearest US territory

Located in the north-west portion of the Pacific Ocean, Iwo Jima is 660 miles south of Tokyo and roughly equidistant from Japan and the US territory of Guam.

3. US forces outnumbered the Japanese by more than 3:1

The invasion pitted 70,000 US combatants against 22,060 Japanese defenders.

4. The Japanese defence was commanded by Lieutenant General Tadamichi Kuribayashi

Kuribayashi’s radical departure from established Japanese strategy shaped the engagement, leading to a drawn out, punishing battle. Prior to Iwo Jima, Japan had defended more directly, opting to face US troops on the beaches in the Gilbert, Marshall and Mariana Islands.

This time Kuribayashi opted to hang back and defend from deeper positions, deliberately delaying the Americans and inflicting as many casualties as possible. In doing so he hoped to damage US spirits and buy more time for Japan to prepare for a looming invasion.

5. The Japanese constructed an elaborate network of tunnels

Kuribayashi’s deep defence strategy involved the construction of 11 miles of fortified tunnels that connected 1,500 rooms, artillery emplacements, bunkers, ammunition dumps and pillboxes. This enabled Japanese soldiers to conduct their stubborn defence from concealed positions and limited the impact of American air and naval bombardment.

Kuribayashi ensured that every part of the island was subject to Japanese fire.

6. America’s pre-landing bombardments were largely ineffective

Ahead of the amphibious assault the US launched a three-day bombardment. This was significantly shorter than the 10-day heavy shelling bombardment requested by Maj. General Harry Schmidt and had limited impact due to the Japanese troops being so thoroughly dug-in.

7. The black beaches that faced American troops were far more challenging than anticipated

US plans seriously underestimated the beach terrain that their landing force would meet at Iwo Jima. Rather than the “excellent” beaches and “easy” progress predicted by planners, the force faced black volcanic ash that failed to provide safe footing, and steep 15-foot high slopes.

8. Kuribayashi waited until the beach was packed with US forces before unleashing the full force of his heavy artillery

The modest response to the initial US beach landings led the Americans to presume that their bombardment had seriously impaired Japanese defences. In fact, the Japanese were holding back.

Once the beach was full of troops and landing craft Kuribayashi signalled the commencement of a heavy artillery assault from all-angles, exposing the invading force to a nightmarish barrage of bullets and shells.

9. Japan’s tunnel system allowed its troops to reoccupy bunker positions

US forces were frequently surprised to find that bunkers they’d apparently cleared with grenades or flamethrowers were swiftly reoccupied thanks to the Japanese network of tunnels.

10. Flamethrowers became a key weapon for the US invaders

The M2 flamethrower was considered by US commanders to be the single most effective weapon in the Iwo Jima engagement. Each battalion was assigned a flamethrower operator and the weapons became the most effective means of attacking Japanese troops in pillboxes, caves, buildings and bunkers.

11. Navajo code talkers played a vital part

From May 1942, the US utilised Navajo code talkers. Because Navajo grammar is so complex, mutual intelligibility and codebreaking is virtually impossible. The speed and accuracy of the Navajo code talkers was indispensable at Iwo Jima – six code talkers sent and received over 800 messages, all without error.

12. US Marines famously raised the Stars and Stripes flag at the top of Mount Suribachi

The summit of Suribachi, which has an elevation of 528 feet, marks the island’s highest point. The American flag was raised there on 23 February 1945, but the US wouldn’t claim victory in the battle until more than a month later, on 26 March.

13. US victory came at a grave cost

Over the course of the 36-day engagement there were at least 26,000 US casualties, including 6,800 dead. This made Iwo Jima the only battle of the Pacific War in which American casualties outnumbered Japanese, although the number of Japanese soldiers killed – 18,844 – was almost three times greater than the US death count.

14. An unprecedented number of US Marines were awarded a Medal of Honour

The ferocity of the fighting at Iwo Jima led to 22 US Marines and five members of the US Navy being awarded a Medal of Honour – the highest military decoration in America – for their bravery during the engagement. That figure makes up more than a fifth of the total 82 Medals of Honour awarded to Marines over the course of the entire war.

15. After the battle, Iwo Jima served as an emergency landing site for US bombers

During the remainder of the Pacific campaign, 2,200 B-29 planes landed on the island, saving the lives of an estimated 24,000 US airmen.

16. Japan surrendered 160 days after its defeat at Iwo Jima

The official surrender took place on the USS Missouri in Tokyo Bay on 2 September 1945.

17. Two Japanese soldiers remained in hiding on the island for six years

They finally surrendered in 1951.

18. The US military occupied Iwo Jima until 1968

At that point it was returned to the Japanese. Today, Japan operates a naval air base on the island, which is also used by the US Navy!