Yesterday afternoon, Ambassador Rich Williamson's family, friends and colleagues bid him farewell at the Kenilworth Union Church in suburban Chicago.

I first met Rich several years ago when he joined Governor Mitt Romney's campaign as a senior advisor on foreign policy. We hit it off from our first telephone call. We worked together to elect the Governor but we bonded over our mutual admiration for America's 40th President, Ronald Wilson Reagan. While I had campaigned for the Gipper as a teenager, Rich worked closely with him as a thirty year old Special Assistant to the President for Intergovernmental Affairs.

It was Ronald Reagan who launched Rich on his impressive and consequential diplomatic career. When long White House hours kept the young husband and father from his wife Jane and their small children, he decided it was time to leave government service. Rich went to the Oval to inform the President. Reagan smiled and asked him if the life of an Ambassador would be more suitable to his family's circumstances. Rich said he would talk with Jane. The next day, after a meeting, Reagan asked Rich to stay behind. Jane had given the okay, so Reagan pulled a list from his drawer, considered it, and told Rich that he would be heading to Vienna to represent the United States at the International Atomic Energy Agency and other UN agencies in the city.

Like the man he worked for and represented as an Ambassador, Rich understood that America was exceptional, the "shining city on a hill". He knew that a policy of peace through strength was the only guarantor of American liberty and that it created hope for millions of freedom-seeking people around the world. Rich was committed to protecting America and promoting democracy and the rule of law abroad. After fighting against nuclear proliferation in Vienna, he served as Assistant Secretary of State for International Organizations in the George H.W. Bush Administration. Rich was a key part of the foreign policy team that so deftly handled the fall of the Soviet Union and reintegration of the captive nations of Europe into the West.

After successful years as a law firm partner and corporate executive, Rich returned to public service in the George W. Bush Administration. His focus as an Ambassador to the UN was human rights. He is perhaps best known for his work as the President Bush's Special Envoy for the Sudan. Rich recognized early on in that position the true nature of the harsh Islamist regime in Khartoum. He added "sticks" to the State Department preferred menu of "carrots" served up to the Khartoum regime. Rich's hard-nosed diplomacy laid the groundwork for the Christians in South Sudan to obtain their freedom and become the world's newest nation.

It was no surprise that Governor Romney, who laid out his own Reaganesque views on American foreign policy in a book entitled, "No Apologies, The Case for American Greatness", was drawn to Rich. Although he was new to many of the folks in Boston, having served as John McCain's principal foreign policy advisor during the Senator's 2000 and 2008 campaigns, Rich's, intellect, foreign policy acumen and sheer enthusiasm for the race made him a key figure on the campaign from the start. He was a pugnacious surrogate who loved mixing it up with cable pundits and had no fear of going head to head with the liberal MSNBC anchors on Mitt's behalf. At the critical moment on September 11, 2012, Rich recognized Benghazi for what it was from the very start - a terrorist attack on the United States. So did Governor Romney. Unfortunately, the mainstream media would not hear anything about the al Qaeda inspired and linked attack on our Ambassador and diplomats in Libya. It did not fit their narrative that the War on Terror had ended the year before in Abbottabad, Pakistan.

Rich took Governor Romney's loss as hard as anyone. He viewed a Romney Administration as an opportunity to rebuild American strength and spread freedom overseas. Rich did not, however, give up following the election. He published, spoke and travelled the globe to promote human rights and the rule of law. I was fortunate to spend a week with him recently in the Republic of Georgia observing the presidential election there for the International Republican Institute, of which Rich served as Vice-Chairman. In Georgia, Rich saw first hand Russia's increasingly aggressive encroachment in the region and was, as usual, prescient in predicting the current crisis in the Ukraine.

Just last week, Rich talked about briefing several potential GOP candidates for 2016. Unfortunately, they will not benefit from his wisdom. Although he was a Republican partisan, Rich's passing on Sunday brought about something unusual in Washington these days: a bipartisan outpouring of sadness for a man who served his country well and fought hard for his party with a smile on his face. Ambassador Rich Williamson will be missed.

Robert C. O'Brien is the California Managing Partner of Arent Fox LLP, a national law firm. He served as a US Representative to the UN and was a Senior Foreign Policy Advisor to Governor Mitt Romney. Robert can be followed on Twitter @robertcobrien. His website is: www.robertcobrien.com