Being a politician or politically active in the Weimar Republic was not an especially safe occupation. You'll no doubt be familiar with some of the more prominent names who were assassinated during the period. Luxembourg, Rathenau, Erzberger, Eisner and Liebknecht are just some of the long list of politicians who were assassinated. Political violence on the lower levels was also not uncommon. During the last years of the Weimar Republic, hundreds of people were killed in street violence.

However, the vast majority of politicians who were assassinated were left wing politicians killed by right wing assassins. The right wing tended to be better organised and supported by more powerful interests than the left. They often got far more lenient prison sentences.

Hitler himself was no exception to the rule. For most of his life he was in the thick of the action. Whether during the First World War where he won the Iron Cross or during his work as an intelligence officer, he never shied away from danger. Politically he was never afraid to get into the thick of the action and as Führer he often made trips to the front, although on many of these trips he was more in danger from his own officers than from the enemy. The Soviets didn't possess the resources to smuggle a bomb disguised as brandy bottles onto his personal plane, but the General Staff of Army Group Centre did.

During his early career, Hitler couldn't rely on formal security, and so had to depend on protection from the SA, who were experienced gutter fighters. On one occasion where a speech was invaded by up to three hundred agitators, a large brawl broke out between them and the fifty SA men in the room. By the time the police had arrived, the SA had driven out the disruptors despite being outnumbered six to one.

As the SA grew and developed in function, a smaller subgroup called the Stosstruppe Hitler was formed, which provided personal security to Hitler. He was often accompanied by up to six armed guards. One man who almost never left his side, Ulrich Graf, potentially saved Hitler's life during the Munich Putsch. As the police opened fire, killing the man next to Hitler, Hitler was knocked to the ground. Graf dived in front of Hitler as he fell, being seriously injured in the process.

When Hitler was sent to prison following the Putsch, the SA were outlawed and Stosstruppe Hitler was disbanded. Following his release, Hitler's personal bodyguard was reformed as the SS. Originally numbering eight men, it rapidly expanded, numbering 100 by the end of 1925.

As Hitler was prone to getting himself into dangerous situations, a high level of security was needed. On several occasions he barely escaped being surrounded by communists, and a number of assassination attempts would be made. When he was travelling, squads of SS would arrive beforehand to check security arrangements. The party headquarters in Munich were always guarded by six SS men, with another eight to ten standing ready in the guard room. Access to Party Headquarters was strictly controlled by passes.

This wasn't always the most effective arrangement of arrangements due to the rather chaotic nature of the Nazi organisation. A plot to kill Röhm enlisted the help of one of the SS guards, who thought better of it before he was due to carry out the attack and informed on the plot. Someone then tried to have the assassin assassinated in the Headquarters but failed. The building was occupied by police on a number of occasions and after the wearing of political uniforms was banned, the police sat outside the headquarters, trying to lure guards out so they could be arrested on public ground.

When Hitler became Chancellor in 1933, he gained access to state resources, and was protected by Police Officers in addition to his own SS guards. This didn't stop people trying to kill him though. In 1933, there were ten plots that were considered feasible by the police, and dozens more less practical plans.

While Hitler did do a lot of public appearances, he was well protected by bodyguards. Areas he was due to visit were cordoned off in advance. SS guards would be deployed to watch rooftops and elevated areas. A sniper would have had to be invisible to escape the notice of dozens of SS guards and get close enough to take the shot. Buildings were placed under guard 24 hours before Hitler was due to arrive and were thoroughly searched before he arrived.

The open topped cars he travelled in had armoured doors and thick glass windows and windscreens, and Hitler would often be followed by a car full of SS bodyguards. However, he travelled with minimal fanfare and protection, preferring anonymity to heavy security. His drivers had orders to accelerate away if danger appeared. Hitler did acknowledge the danger of open topped cars, especially after Heydrich was assassinated while driving in one in 1942. For travelling long distance he had a special armoured train. When flying, he travelled in a plane with an armoured compartment, and a special ejector seat with a parachute.

While Hitler was heavily protected, there was still a heavy element of luck. There were a number of embarrassing breaches in his personal security, and he only escaped death by the skin of his teeth on a number of occasions. Apart from the 20th of July explosion, the Army officer plotters had a live bomb in Hitler's presence twice, and on three or four other occasions would have killed him if coincidence hadn't prevented it.

Hitler was out in public a lot, but he wasn't unprotected. The SS and regular police forces were capable planners and took the appropriate precautions.

Most of this information and a whole lot more technical detail about Hitler's protection can be found in:

Peter Hoffmann, Hitler's Personal Security.

Hope this helps, let me know if you have any more questions!