Secretary of State Rex Tillerson hailed the late German Chancellor Helmut Kohl as "true statesman" and critical friend of the United States.

"His work helped advance our shared vision of building a peaceful and democratic Europe," Tillerson said Saturday.

Kohl died Friday. His 16-year-tenure as chancellor was second only to Otto von Bismarck, who oversaw the unification of Germany in the 19th century; and like Bismarck before him, Kohl was instrumental in re-unifying East and West Germany following the collapse of the Soviet Empire.

"Chancellor Kohl was a friend to the United States during a transformative period for Germany and Europe as a whole," Tillerson said.

In tandem with reunifying Germany, Kohl also labored to establish a common currency within the eurozone; the move helped ease French opposition to his reunification plans. Former President George H.W. Bush, Kohl's partner in the reunification process, hailed him as "one of the greatest leaders in post-war Europe" in a Friday salute.

"Like so many who bore witness to the unspeakable depravity and hardships of that time, Helmut hated war -- but he detested totalitarianism even more," Bush said. "And so he would devote his public life to strengthening the institutions of democracy in his homeland, and beyond. Working closely with my very good friend to help achieve a peaceful end to the Cold War and the unification of Germany within NATO will remain one of the great joys of my life."

Kohl mentored his eventual successor, Angela Merkel, but he lost power in 1998 and then she completed his expulsion from the party due to a campaign donations scandal. "[I]t was Merkel who felled him with a lethal bite to the jugular: She penned an article on the front page of a national newspaper calling for the party to drop him," Brookings Institution senior fellow Constanze Stelzenmüller wrote in the Washington Post. "A breathtaking act of political risk-taking, it made her the leader of the pack. In 2005, she was elected chancellor."

That conclusion to his career did not diminish his legacy, in Merkel's assessment. "For Germans, he was a stroke of luck," she told the BBC on Friday. "I bow before his memory."