Question: What was the Allies' nickname for the German general who set up a defensive line in the Apennine Mountains during World War II?

Context paragraphs:
Bernhardt Line: The Bernhardt Line (or Reinhard Line) was a German defensive line in Italy during the Italian Campaign of World War II.  Having reached the Bernhardt Line at the start of December 1943, it took until mid-January 1944 for the U.S. Fifth Army to fight their way to the next line of defences, the Gustav Line.  The line was defended by XIV Panzer Corps ("XIV Panzerkorps"), part of the German Tenth Army ("10.  Armee").

Fifteenth United States Army: The Fifteenth United States Army was the last field army to see service in northwest Europe during World War II and was the final command of General George S. Patton.  The Fifteenth Army served two separate missions while assigned to the area.  During the later stages of World War II its mission was training and rehabilitating units and acting as a defensive line against counterattacks.  After the war its mission was to carry out occupation duties and to gather historical information related to the European Theater of Operations, or ETO.  The Fifteenth Army was inactivated in 1946 and has not been activated since.

Battle of Aachen: The Battle of Aachen was a major combat action of World War II, fought by American and German forces in and around Aachen, Germany, between 2–21 October 1944.  The city had been incorporated into the Siegfried Line, the main defensive network on Germany's western border; the Allies had hoped to capture it quickly and advance into the industrialized Ruhr Basin.  Although most of Aachen's civilian population was evacuated before the battle began, much of the city was destroyed and both sides suffered heavy losses.  It was one of the largest urban battles fought by U.S. forces in World War II, and the first city on German soil to be captured by the Allies.  The battle ended with a German surrender, but their tenacious defense significantly disrupted Allied plans for the advance into Germany.

Trasimene Line: The Trasimene Line (so-named for Lake Trasimene, the site of a major battle of the Second Punic War in 217 BCE) was a German defensive line during the Italian Campaign of World War II.  It was sometimes known as the Albert Line.  The German Commander-in-Chief (C-in-C), "Generalfeldmarschall" Albert Kesselring, used the line to delay the Allied northward advance in Italy in mid June 1944 to buy time to withdraw troops to the Gothic Line and finalise the preparation of its defenses.

South-east wall: The South-east wall (German: "Südostwall") (also known as Reichsschutzstellung) was a system of fortifications planned by Nazi Germany in the late stages of World War II to extend along the Little Carpathians and Lake Neusiedl southwards to the River Drau.  Not a wall in the true sense of the word, the South-east wall was rather a series of German batteries and anti-tank ditches built at strategic locations alongside the southeastern border of the German Reich in 1944/45 with the intention of stopping the Red Army.  The defensive line was only partly finished when the Red Army reached the line in March 1945, and merely slowed the speed of their offensive.  The Red Army broke through the line at the beginning of the Vienna Offensive.  Vienna is located only 35 km west of the defensive line.

Albert Kesselring: Albert Kesselring (30 November 1885 – 16 July 1960) was a German "Luftwaffe Generalfeldmarschall" during World War II.  In a military career that spanned both World Wars, Kesselring became one of Nazi Germany's most skilful commanders, and one of the most highly decorated, being one of 27 soldiers awarded the Knight's Cross of the Iron Cross with Oak Leaves, Swords and Diamonds.  Nicknamed "Smiling Albert" by the Allies and "Uncle Albert" by his troops, he was one of the most popular generals of World War II with the rank and file.

Siegfried Line: The original Siegfried Line (German: "Siegfriedstellung" ) was a First World War line of defensive forts and tank defences built by Germany in northern France during 1916–17 as a section of the Hindenburg Line.  In English the term "Siegfried Line" commonly refers to the "Westwall", the German term for a similar Second World War-era defensive line built further east during the 1930s opposite the French Maginot Line.  This line stretched more than 630 km and featured more than 18,000 bunkers, tunnels and tank traps.  The network of defensive structures stretched from Kleve on the border with the Netherlands, along the western border of the old German Empire, to the town of Weil am Rhein on the border to Switzerland.  It was planned in 1936 and built between 1938 and 1940.

Winter Line: The Winter Line was a series of German and Italian military fortifications in Italy, constructed during World War II by Organisation Todt and commanded by Albert Kesselring.  The series of 3 lines was designed to defend a western section of Italy, focused around the town of Monte Cassino, through which ran the important Highway 6 which led uninterrupted to Rome.  The primary Gustav Line ran across Italy from just north of where the Garigliano River flows into the Tyrrhenian Sea in the west, through the Apennine Mountains to the mouth of the Sangro River on the Adriatic coast in the east.  The two subsidiary lines, the Bernhardt Line and the Hitler Line ran much shorter distances from the Tyrrehnian sea to just North East of Cassino where they would merge into the Gustav Line.  Relative to the Gustav Line, the Hitler Line stood to the North-West and the Bernhardt Line to the South-East of the primary defenses.

Prince Christoph of Hesse: Christoph Ernst August of Hesse (Frankfurt, 14 May 1901 – Apennine Mountains near Forlì, 7 October 1943) was the fifth son of Prince Frederick Charles of Hesse and Princess Margaret of Prussia.  He was a German SS officer killed accidentally during World War II.

Gothic Line: The Gothic Line (German: "Gotenstellung" ; Italian: "Linea Gotica" ) was a German defensive line of the Italian Campaign of World War II.  It formed Field Marshal Albert Kesselring's last major line of defence along the summits of the northern part of the Apennine Mountains during the fighting retreat of the German forces in Italy against the Allied Armies in Italy, commanded by General Sir Harold Alexander.

Supporting paragraphs: Gothic Line Albert Kesselring
Answer: "Smiling Albert"