What caused the shortages in such components was the relentless Allied bombing campaign that sought to disrupt all flow of German war-making capabilities. This meant attacking key oil reserves, weapons stores, production facilities and transport routes that ultimately served these production facilities. Bridges and railways were high on the priorities list. The German defense was effective but only up to a point for with each passing month, the war produced an ever smaller German Empire to defend and air superiority eventually slipped away from the Luftwaffe. Along with that fact, German-held factories ultimately fell into Allied hands as territories were inevitably lost and vital supply routes became furthermore disrupted in the process, delaying production of key valuable systems such as gun barrels, ammunition and engines. At peak production in December of 1944, twenty Jagdtigers rolled off of German assembly lines. From thereon, totals of no more than thirteen were reached (February 1945) and only three were completed in March of 1945.
The Jagdtiger was an impressive design for its time and went on to become the heaviest armored vehicle fielded in quantity during all of World War 2. She sported no less than 250mm of thickness across her frontal facing alone, ensuring that the crew was relatively safe from enemy anti-tank guns and projectiles from this direction. Regardless of what main gun was fitted, she always held the potential of knocking out any Allied tank at distance with a first shot. The crew was given one or two MG 34 general purpose machine guns for anti-infantry defense and to combat low-flying attack aircraft with 3,300 rounds of ammunition. Power was derived from a single installation of a Maybach HL 230 P30 series V12 liquid-cooled, gasoline-fueled engine developing up to 700 horsepower. While inherently powerful on its own, the engine was taxed by the sheer weight of the Jagdtiger frame and allowed for a top speed of just 21 miles per hour with an operational road range of 62 miles (this decreased to 43 miles when attempting off-road travel). The chassis was suspended on a torsion bar system across eight overlapping road wheels to a track side. She fielded a length of 35 feet to the tip of the main gun barrel and was 12 feet in width and some 9.2 feet high - a rather large profile to say the least. "Zimmerit" anti-magnetic paste - a special anti-tank mine coating - was applied to outgoing factory models up until the end of September in 1944 (Zimmerit was noted by its "ribbed" like appearance across armor facings on German tanks).
Externally, her original King Tiger design shown through with her sloping front glacis plate, partially-skirted road wheels and rear-mounted engine. One key different in identifying the Jagdtiger design was the fixed superstructure sporting the thick gun mantlet at the barrel base and the superstructure's sloped side facings. The fixed nature of this arrangement meant that traverse was extremely limited and forced the crew to point the entire tank in the direction of the enemy - a key disadvantage in any tank battle. This essentially made the Jagdtiger a mobile gun platform that served better as a defensive implement than an actual tank hunter/killer. All things considered for Germany late in the war, the defensive-minded nature of the design was actually suitable for the defensive war she now found herself in.
There was no denying the inherent value of the Jagdtiger - her firepower was second to none and her armor protection proved excellent. However, all of these features came at a price and the limitations inherent in the King Tiger design itself soon shown through. The Jagdtiger fought to maintain consistent and useful speeds, particularly when heading off-road to which a measly 9 miles per hour could be reached in prime conditions. This was more akin to the ponderous tanks being fielded in World War 1 than anything the modern battlefield should have seen in this point in history. The lack of a traversing powered turret was a true detriment to the crew yet ultimately sped up production time. Only about 40 of the large 128mm projectiles could be carried aboard, limiting her long-term usefulness in a stand-up firefight, and projectile and explosive charge were loaded individually which resulted in a slower rate-of-fire than desired. The heavy nature of the chassis, hull and superstructure combined meant that the engine worked harder than it should have and could easily lead to mechanical issues in-the-field in terms of reliability. Couple this with limits in spare parts and accessibility to these parts and one can quickly draw up a recipe for failure. The power-to-weight output also meant that the engine burned more fuel than what was tactically adequate, limiting her operational reach to the extreme. With all of these restrictive elements in hand, the Jagdtiger really did serve the more logical role of a defensive gun fixture or support for infantry spearheads. She could be used to wait in ambush for columns of primed enemy tanks to appear on the horizon or supports ground offensives as an assault gun. However, once her position had been overrun, the type was rendered rather useless thereafter. Additionally, direct hits to the side or more vulnerable rear facings (no more than 80mm thick) through a combined flanking maneuver could yield a destroyed or even disabled Jagdtiger, ultimately forcing surrender by the crew. Some were blown up with explosives by retreating crews.
The tenure of the Jagdtiger ended with the capitulation of Germany in May of 1945. By now, Hitler was dead and had passed on his power to trusted authorities - though these persons would recognize a losing war effort when they saw one and the unconditional surrender of Germany spawned VE Day celebrations on May 7th/8th. The Jagdtiger was captured by the Allies and evaluated for a time after the war. An interesting testament to her powerful design, there was never really a true answer to the Jagdtiger from the Allied point of view. Her limited production and tactical capabilities certainly played well into Allied hands and worked against the tactics of the German Army - an army that was initially build on speed and numbers to achieve ultimate victory. Speed and numbers were not the Jagdtigers strong points.
Only two German Army units ever fielded the Jagdtiger - these being schwere Panzerabteilung 512 and Panzerjagerabteilung 653.
In the end, the Jagdtiger was anything but the tank-hunter that it was advertised to be. The system ended up faring better as a stationary artillery platform, offering up infantry support or holding ground as a sort of armored and mobile "bunker" than it was at chasing down and destroying the faster-moving American, British and Soviet designs. Though no Allied armor could withstand the might of the 128mm projectile of the Jagdtiger's main gun, the Allies still held the advantage of being on the offensive by the time the Jagdtiger was ready for action.