British barrister Karim Khan was sworn in on Wednesday as the new prosecutor at the International Criminal Court.
Mr Khan, 51, faces huge challenges, including ongoing investigations in the Palestinian territories, Afghanistan and the Philippines, as he begins his nine-year tenure at the world's only permanent war crimes court.
He inherits a bulging case file from his predecessor Fatou Bensouda, who extended the ICC's reach so dramatically that she was hit by US sanctions. She also suffered a series of high-profile failures.
As he took his oath at The Hague, Mr Khan said his team must focus on getting to the truth to build stronger cases and achieve better results in the court room.
"Opening preliminary investigations is a start but we have to perform in trial," he said.
"We cannot invest so much, we cannot raise expectations so high and achieve so little so often in the court room.
"As an office we need a greater realisation of what is required by the burden of proof and the obligation to prove a case beyond reasonable doubt.
"During my term my aim is to build upon what works but also to repair what has broken, to rejuvenate, to revive, in the quest for greater efficiency and impact."
Already short of resources, the International Criminal Court is dealing with 14 full investigations and eight preliminary examinations.
Last year, an independent review criticised a "culture of fear" in the prosecutor's office and called for reforms to improve the workplace environment.
On Wednesday Mr Khan vowed to urgently address issues of harassment and to ensure gender and geographical equality in his new office.
"To the staff, you have a right to work in an harassment-free working environment and I intend to start addressing that from today," he said.
"I hope with the help of the staff we can make this a reality. With this regard in my view the current gender and geographical imbalance in the office, particularly the gender imbalance in the highest echelons of the office, must be treated as an urgent operational priority, requiring immediate correction.
"This is not some favour to different parts of the world or to women, this is a requirement of good management and good justice."
He asked survivors for their patience while improvements are made and promised to "tell them the unvarnished truth" at all times.
Mr Khan said he wanted trials to take place in the regions where the alleged crimes were committed and urged non-member states to engage with him.
"To non-state parties I say that I wish to include you in my engagement in this joint quest for justice," he said.
"My conviction is that we can find common ground to eradicate genocide, crimes against humanity and war crimes."
He said that it was a "great honour" and he was "truly and sincerely humbled" to have been given the role.
Judge Piotr Hofmański, President of the ICC, warned Mr Khan about the pressure he will face in the role after his predecessor was sanctioned by the US over her decision to examine war crime allegations in Afghanistan, including by US troops.
"The prosecutor takes the initiative to launch investigations and is responsible for the way prosecutions are conducted and how evidence for the prosecution is selected," he said.
"The ultimate responsibility lies with the prosecutor and he or she is the one who will face the public's price and blame.
"It was the ICC's Fatou Bensouda who faced unprecedented consequences from her work by way of sanctions. This was a stark reminder of the kind of pressure the prosecutor might face."
Mr Khan, who cut his teeth as a top international defence lawyer, was previously head of the UN's ISIS war crimes unit.
Under his tenure many Yazidis were finally able to bury their loved ones this year.
