A newly published book, Tomorrow’s Battlefield: US Proxy Wars and Secret Ops in Africa, recounts incidents of sexual assault and misconduct by US military personnel in Africa, some of which has led to deaths.

Investigative reporter Nick Turse also talks about a far-reaching but largely secret expansion of the US military role in Africa.

Last year, the United States carried out 674 military activities across Africa, compared with 172 in 2008.

“US troops were carrying out almost two operations, exercises or activities — from drone strikes to counter-insurgency instruction, intelligence gathering to marksmanship training — somewhere in Africa every day of 2014,” writes Mr Turse.

In addition to having conducted direct combat operations in Libya, the US has assisted French forces fighting in Mali and the Central African Republic.

The US also launches missile strikes on targets in Somalia and is assisting African troops hunting the Lord’s Resistance Army in Central Africa and Boko Haram in Nigeria. American military personnel likewise operate from Kenya, Uganda and Ethiopia.

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He also recounts incidents of sexual assault and sometimes fatal misconduct on the part of US military personnel in Africa. Mr Turse reports incidents of misconduct involving drugs and prostitutes by US soldiers stationed at Camp Simba, which he refers to as “a hush-hush military outpost” at Manda Bay in Kenya.

In 2010, a US Army National Guard sergeant was found dead at the Sarova Whitesands Beach Resort in Mombasa.

According to official documents obtained by Turse through the US Freedom of Information Act, the soldier had returned to his room in the resort with a woman from a nearby bar where prostitutes and drugs were said to be plentiful. A US Army investigation later determined, Mr Turse reports, that the sergeant had “accidentally died of multiple drug toxicity after drinking alcohol and using cocaine and heroin.”

In 2013, a US National Guard soldier deployed at Camp Simba got drunk, stole a pistol and shot a superior officer. The soldier was himself then shot in the leg and later surrendered.

He also documents a number of cases of sexual assault by US military personnel stationed in Djibouti.

The East African country plays an outsize role in US military strategy in Africa.

Djibouti has served for the past several years as the headquarters of the US Combined Joint Task Force-Horn of Africa.

In 2011, according to a Pentagon report cited by Mr Turse, a non-commissioned officer sexually assaulted a female subordinate at a US base in Djibouti presumed to be Camp Lemonnier.

That same year, an enlisted woman reported being raped by a fellow US service member in Djibouti. Another attack on an enlisted woman is said to have taken place in Djibouti in 2012.

A classified criminal investigation file obtained by Mr Turse indicated that in July 2012, the US commander of a counterterrorism task force based in Djibouti sought to touch the private parts of a woman with whom he was riding in a car. The commander, Maj Gen Ralph Baker, had been drinking heavily at a party and was returning to Camp Lemonnier at the time of the incident, Mr Turse reports.

Asked to comment on Turse’s reports of misconduct by US military personnel in Africa, Africom spokesman Benjamin Benson wrote in an email to The EastAfrican: “US military members are held to the highest standards of our professionalism and national values. We emphasise that our people are ambassadors for the US in our foreign host nations and must emulate the morals and values that make our nation strong.”