Of course they did. As a Pole I feel obliged to write about polish attempts. Unfortunatelly I'm not a historian but yet I hope my post will not be considered unprofessional.

British did not perform assasination attemts because feared that it would escalate and there would be counter-assasinations in Britain. Soviets at the beginning were Hitler's allies and after 1941 wanted the war to be as long as possible to expand into west. So living dtubborn Hitler was convenient to them.

On the 5th of November 1939 victory parade took place in Warsaw, Poland. Hitler came there as a conqueror and as a head of the german state.

Germans have taken hostage 400 people including president of Warsaw Stefan Starzyński for safety. This parade was well documented by germans due to it's propaganda value. film

This assasination attempt was prepared by major Franciszek Niepokólczycki who was a commander of apper battalion in Modlin (polish fortress north east of Warsaw which has longest building in Europe, second worldwide).

Before 28.09 (capitulation of Warsaw) he joined newly formed underground organization SZP (Service for Poland's Victory).

By the end of September he was ordered to mine crossing of 2 major Warsaw streets: Nowy Świat and Aleje Jerozolimskie. Polish general Tokarzewski-Karaszewicz who ordered this assasination assumed if there would be a parade it had to run through this crossing.

On the 25th of September explosives (TNT) were being transported from ammunition warehouse under heavy bombing (600 tons of bombs were dropped on Warsaw that day + heavy artillery fire)

One of the known guys (this action was so secret we know very little who participated) who were obliged to transport this materials was Dominik Żelazko. He stated that they had this TNT pulled on a wagon by a horse.

This load was well hidden in anti-tank trench for few days and after capitulation of Warsaw.

Then Lieutenant Franciszek Unterberger and capitan Edward Brudnicki from this sapper battalion worked on planting this bomb with no german suspition due to massive sapper work in the city. 250kg of explosiveson each side of the crossing were planted.

On 4th of November mjr Niepokólczycki reported to gen. Tokarzewski that all is ready.

Why this plan failed? German troops were cleaning the streets of the people. Unfortunatelly they were able to destroy one piece of reconnaissance chain. Mjr Niepokólczycki was not able to get to ambush site due to all roads being closed with death penalty to anyone who would show on the streets and in the windows. Lack of commander and reconnaissance made guy sitting with detonators in nearby caffe without orders. And he had little time to make decision on his own because Hitler was in a hurry nad only passed bombsite 1 time instead of 2 and speeding due to being late.

In part because the CIA did not exist until 1947 when the National Security Act of that same year created the agency.

Hitler's house the Berghof was also the target of a significant raid by the Royal Air Force in April, 1945, which would generally be described as a decapitation strike today.