Breaking the Nazi Codes

While Poland was behind Germany and other European powers in most areas of military doctrine and technology, it was well ahead in one area – breaking of German codes. Germany was well ahead in cypher machines, with the first Engima machine developed for civilian purposes (at least officially); in 1930 a military version was constructed as a part of rearmament plans. The Poles immediately set up a special German Branch in their military cipher department to work on deciphering the German codes. And in 1929., the director of the Poznan Mathematics Institute recruited several brilliant young mathematicians to work closely with the cipher bureau. Despite only having a commercial Enigma machine to work with, by February 1933. the code had been decrypted and the Polish General Staff was able to commission the construction of fifteen replicas. A year later they were able to read the highly secret messages about the Night of the Long Knives.

Despite new generation of Enigma machines, in January 1938. the Poles were able to read 75% of Wehrmacht’s cable traffic. But the change in cypher on 15^th September 1938. meant that new way of reading the Enigma was necessary, leading to development of the Bombe. It was a complex of six Polish Enigma machines, connected with additional devices and transmissions. Until the beginning of the war the Poles kept improving ways of breaking German codes, and their know-how was shared with Britain and France in January and again in July 1939. An Enigma machine was taken back to both London and Paris.

Moves Towards the Invasion

Fundamentals of the Polish foreign policy were laid down by Pilsudski and implemented by his foreign secretary Jozef Beck. Fundamental idea was that if Poland was to remain independent, it would need to balance between Germany and USSR while also cooperating with Romania, Baltic states and France. In 1932. a non-aggression treaty was signed with USSR, and in 1934. with Germany. Pilsudski observed that this latter agreement “removed Poland from Germany’s hors d’oeuvre to her dessert”.

But just as it was obvious to Poland that Germany will attack sooner or later, so it was obvious that USSR was only waiting for an opportunity to reassert its dominance in the Eastern Europe. Poland thus was entirely justified in refusing to join the Franco-Soviet Pact in 1935. Yet in 1936., when German troops marched into the Rhineland contrary to the terms of the Treaty of Versailles, Beck informed the French Ambassador in Warsaw, Léon Noël, that Poland was ready to fulfil her obligations to France should war break out.

However, British policy of appeasement complicated the Polish situation. Britain and France were no longer reliable partners, yet doors for cooperation had to be kept open while avoiding alienating either Germany or USSR. Hitler had no doubts that Poland would attack Germany should the opportunity arise:

Our agreements with Poland will remain valid as long as Germany’s strength will remain unshakeable. Should Germany have any setbacks, then an attack by Poland against East Prussia perhaps also against Pomerania and Silesia, must be taken into account.

Hitler’s annexation of Austria in 1938. did not present an immediate challenge to Warsaw, and in fact many in Poland had hoped that it would reduce tensions and deflect Germany from demanding the return of Danzig and the Corridor. But General Sosnkowski, the former Polish War Minister, predicted accurately that the fall of Austria would lead to the destruction of Czechoslovakia, Poland and then France. As soon as Hitler started working on annexing Sudetenland, Poland began exploiting each shift in direction by Britain, France and Germany. But it was a difficult task, as Poland had to resist joining the Axis and guarantee Polish neutrality while still leaving door open for cooperation with the UK and France.

Once Chamberlain and the French Prime Minister Daladier had conceded at Berchtesgarden in September 1939 that the Sudetenland should, in principle, be awarded to Germany, Poland – backed by Germany – formally laid claim to Teschen. By 24 September about 40,000 troops were concentrated in the Teschen area. At the same time the Trans-Olzan Volunteer Corps was formed, which was affiliated to the Polish League of Silesian Insurgents. 10,000 volunteers enrolled in Warsaw and another 15,000 in Lodz. The Czech Government attempted to be conciliatory and agreed in principle to the transfer of Teschen, but tried to avoid being tied down to a precise date.

Munich Agreement, signed on 30 September, confirmed the cession of Sudetenland to Germany but made no decision regarding Polish and Hungarian claims. For Poland, especially pressing was the danger of Germany seizing the industrialized district of Teschen. Beck sent an ultimatum to Prague demanding cessation of Teschen within ten days, else Poland would use force. Under pressure from Britain and France, Czechs agreed to cessation. But these events did little to ease German – Polish tensions, and Poland also had problems with Ukrainian nationalists and other minorities within its borders.

Danzig and the British Guarantee

Munich Conference had shown the danger that Poland might become the next victim of a “peace settlement” between the great powers. The key concessions Hitler wanted from Poland were the return of Danzig to the Reich and the construction of an extra-territorial motorway across the Polish Corridor to East Prussia. In return for this he was ready to contemplate some eventual compensation for Poland at the expense of the USSR in the Ukraine. At talks in Warsaw in January 1939. Ribbentrop proposed cessation of Danzig and construction of the motorway to be balanced by ceding Poland the territory taken from USSR in a joint German-Polish attack against the USSR, specifically the Subcarpathian Ruthenia. Beck refused to give away tangible rights for mere guarantees, but left the issue open with possible future talks.

Aware that Germany might soon run out of patience, Beck decided to reinvigorate the alliance with France, if possible with British backing. France itself, faced with Italian claims to Nice, Corsica and North Africa, was eyeing the possibility of network of East European alliances, and Poland fell neatly into these plans. In the UK, Lord Halifax began to see Poland’s value as a check to German expansion in Eastern Europe.

On 15 March Germany broke the Munich agreement by occupying Bohemia and creating a protectorate over Slovakia. On 19 March Lithuania was told to hand over Memel ‘graciously’ to the Reich, and two days later Ribbentrop informed the Polish Ambassador in Berlin that Poland must realize that she could only remain a national state if she worked for a ‘reasonable’ relationship with Germany. Poland now received unexpected support from Britain. Chamberlain warned Germany against further aggression, and after Germany demanded monopoly on Romanian oil, British set to form an anti-German bloc in Eastern Europe. The French wanted Poland to give a guarantee of assistance to Romania, but Poland required similar guarantee for herself from the Western powers before committing.

German occupation of Memel on 22 March caused Poland to mobilize, but Hitler still wanted to avoid confrontation, to give Polish government time to make concessions and to head off any agreement between London and Warsaw. Ultimate goal however was still to restore German borders to 1914. state and reduce Poland to a non-factor.

On 31 March, Chamberlain announced in the House of Commons that

in the event of any action which clearly threatened Polish independence, and which the Polish Government accordingly considered it vital to resist with their national forces, His Majesty’s Government would feel themselves bound at once to lend the Polish Government all support in their power. They have given the Polish Government an assurance to that effect.

But while Great Britain (and France) were thus firmly committed to Polish independence, the guarantee was at best a diplomatic deterrent as it was not an actual military alliance. And because it was unilateral, it could be revoked at any time. It was thus a symbolic gesture at best, but one that gave Poland a hope for an actual alliance. Indeed, Colonel Beck, the Polish Foreign Minister, visited London on 2 April with the hope of converting the British guarantee into an alliance or at the very least of defining it more precisely. But he did not mention lack of progress on German-Polish negotiations over Danzig, as he feared British might then revoke their guarantee.

It is thus not surprising that Germany did not see the guarantee as a serious obstacle to invasion of Poland.

German Response

Realizing that after the British guarantee Poland would not give up Danzig or become a puppet state, Hitler ordered military preparations for an invasion of Poland. Directive for Fall Weiss or “Operation White” was issued on 11 April, while the operation was to begin at any date after 1 September. Aim was to take Danzig, destroy Polish armed forces, and if possible limit the war to Poland only. Hitler believed that attempt to gain living room from USSR would be faced with hostility from Britain and France, while Poland would not be a reliable ally. Poland had to be attacked at the first opportunity, but Hitler – at a meeting with generals on 23 May 1939. – added that Germany must prepare for a war of ten to fifteen years.

The British guarantee strenghtened Polish resolve to fight. It also ensured that any Polish-German conflict would lead to a global war, which was to Polish advantage. In May, the Polish Minister of War, Lieutenant General Tadeusz Kasprzycki went to Paris, where, on the 19th, he signed a military protocol committing France immediately in the event of a German attack on Poland. The French Army would begin limited action against the Germans within three days of mobilization and a major land operation some twelve days after that, which would entail an attack on Germany across the north-eastern French frontier with thirty-eight divisions. This however was only to become valid after the political guarantee had been signed – and political convention was only signed after the war broke out on 4 September.

On 27 May the French Air Force also promised to attack Germany as soon as war broke out. But this was an empty promise, as the French Air Force had no intention of carrying out offensive operations, and decided to act only in defense of French territory. This however was hidden from the French government. At the end of May, British military mission was sent to Poland to discuss what aid could be sent to Poland in the event of war. It was clear that no British military (or naval) support would be forthcoming, and only agreement reached was that three Polish destroyers would sail away to Britain as soon as the war broke out. Only RAF would provide aid by attacking military targets in Germany. Second series of discussions in July was merely a way of reassuring Poland, with nothing concrete being concluded.

Over the summer, the Air Ministry gave thought to opening air bases within Poland. But these could be supplied only in one of three ways:

1. By sea to Murmansk and rail via Leningrad.
2. Through the Suez Canal to Odessa and thence by rail via the USSR to Poland.
3. By sea to Basra and thence by rail through Turkey to the Black Sea and across the Black Sea to Odessa.

Air Ministry also drew up plans for basing two Wellington squadrons in Poland which would land alternately in Britain and Poland after the initial operations. The Poles would be required to provide one main base and a satellite aerodrome, ground defences and signals communications. RAF was able to offer 100 – 150 Fairey Battles (single-engined light bombers) immediately, and further 100 on a later date. No Spitfires or Hurricanes could be offered, but Vickers was allowed to release to Poland the plans for Hurricane III.

The Poles did not raise the key question of finance, despite desperately needing money, as Beck felt it would have been undignified. Poland had only sufficient reserves of armaments to equip in the first instance about fifty-four infantry divisions, two cavalry divisions and a small number of mechanized formations. Once active operations started, Polish industry had only sufficient capacity to maintain about ten divisions in active operations. Losing Silesia would severely reduce even this already limited capacity.

Poland thus needed to build up her stocks of ammunition and raw materials within the Central Industrial District. But this would only delay the inevitable. Thus, Poland also needed loans to buy equipment, raw materials and enlarge her own industrial base. Even so, with Germany able to cut off access to Danzig, delivery would be difficult. And despite French support, Britain turned down Polish requests for aid, on the grounds that it would trigger requests by other states.

Eventually, the Government did relent and, together with France, offered help to Poland. But even then the Treasury wanted to attach conditions: devauling zloty as well as Poland accepting the International Coal Agreement. Only on 7 September did Britain give Poland a cash advance of 5 million pounds. Thus, it is no surprise that Germany did not take British guarantee to Poland seriously.

Polish War Plans – “W” and “Z”

Until 1926., Poles had planned for a two-front war against Germany and USSR both. But in 1926., Pilsudski judged that main threat was that of USSR, and Plan W was drawn up. This also determined the shape of the Polish army: lack of roads in the eastern areas of Poland and in the USSR meant that cavalry was crucial for tactical mobility, and thus had to be retained.

In 1938., the General Staff began to modernize the mobilization plans. New Plan W was a general plan applicable for either war against USSR or Germany. Plan W was a staggered mobilization plan intended to avoid the provocative effect of full mobilization. Plan Z was intended specifically for defense against Germany, which would focus the forces against Germany:

• Army Warsaw, grouped just south of the East Prussian frontier.
• Army Pomorze, based in Torun.
• Army Poznan, stationed just east of Poznan.
• Army Lódz-Czestochowa, concentrated on a line to the east of Lodz and Czestochowa.
• Reserve Army, grouped between Kutno and Warsaw.

Plan was based on expectation that the main German attack would come from the north-west, with supporting attacks though Silesia and East Prussia. The gist of the Polish response was for a pre-emptive Polish strike against East Prussia, while the main German attack would be contained by the Armies Pomorze and Poznan with the Reserve Army in support. A German thrust from Silesia was to be countered by the Lodz-Czestochowa Army. The plan however was rapidly rendered obsolete as Germany seized Bohemia and Moravia and made Slovakia into a puppet state.

GISZ decided to adop the original Plan Z but create another army to cover the Carpathians and act as a reinforcement for the Silesian front. The plan consisted of three phases:

• The frontier forces would fight a delaying action along the borders, so that the bulk of the Army would have time to be mobilized.
• When this was completed the Germans would be confronted on the actual line of defence.
• The Reserve Army would be deployed in the sector that was most under threat.

Goal was to delay the enemy until the French and the British could relieve pressure in the West. This plan was not – despite common historical misconception – a plan of static defense (nor was the French Maginot line such a plan). Frontier armies were to act as a screen to allow completion of mobilization. But this required seriously overstretched frontier forces to hold back the Germans until mobilization could be completed. Faced with German armor and air force, this task would prove impossible. Old structural and organizational problems had also remained unresolved: Administration was still divided between the General Staff and the General Inspectorate, and Rydz-Smigly had centralized command and control to the point of making it impossible to carry out. He also restricted information available to army commanders, and thus none of the commanders had any idea of the overall plan of the campaign.

Polish Air and Naval Plans

Air Force plan had combat elements regrouped so they could deal with the anticipated combat demands of the Army High Command. Air assets were divided into the Dispositional Air Force, an independent tactical formation composed of two brigades: the Pursuit Brigade, which was composed of five fighter squadrons, whose role was to defend Warsaw, and the bomber brigade. This was composed of five Karas light bomber and four Los medium bomber squadrons. Each Army also had squadrons attached to it for reconnaissance and protection operations.

The Navy and the Merchant Marine were also placed in the state of heightened awareness. In 1936., all Polish shipping companies were ordered to ensure that the decks of their ships were strengthened to accommodate artillery as well as heavy machine guns. On 30 March 1939 a law was passed by the Sejm requiring all shipowners to place their vessels at the disposition of the Government in the event of war. In late August, all ships were warned to stay out of Baltic, and to seek British, French, or neutral ports. From May onwards all ships returning to Gdynia were to have a minimum ten- to fifteen-day supply of bunker oil and food to allow a rapid departure for British waters, should war break out. Destroyer and Submarine Divisions were put on a state of alert from March 1939. onwards. In the event of war, destroyers were to head for British ports. The task of the submarines was to interdict the passage of German troopships and transports to East Prussia, while the three boats with mine-laying capacity were to lay mines in the Gulf of Danzig (Gdansk).

Fall Weiss

In May, General Rundstend and his staff, responsible for planning the attack on Poland, attempted to forecast what the Polish plan of operations would be. They correctly predicted that Poles would attempt to defend the valuable border territories. Their main fear was that the bulk of the Polish Army would then be able to withdraw behind the Narew–Vistula–San line without having been decisively defeated.

German plan for invasion of Poland was rather simple: surprise invasion was to prevent the regular mobilization of the Polish Army. Bulk of the Polish Army was to be destroyed west of the Vistula–Narew line by a concentric attack from Silesia on the one side and from Pomerania/East Prussia on the other.

For this purpose, German forces would be divided into two Army Groups, North and South. The former was composed of two armies, the Third under von Küchler and the Fourth under von Bock, which came to 630 000 men. Sufficient bridging material was to be assembled in the course of the summer to construct four bridges over the Oder and the Vistula.

On the first day of hostilities – ‘Y Tag’ – the Army Group North was to bypass Danzig and restore the territorial link between East Prussia and the rest of the Reich. Polish forces in the Gdynia-Danzig area would be destroyed later, while Danzig would be annexed to the Reich with the help of local paramilitary forces. Most of Third and Fourth Armies were to move eastwards to Vistula and then Warsaw.

Army Group South was composed of three armies, the Eighth under Blaskowitz, the Tenth under Reichenau and the Fourteenth under List, a grand total of 882 000 men under the overall command of von Rundstedt. The Tenth Army was to attack from Silesia towards Warsaw. In order to spare Upper Silesian industry from destruction, Tenth Army was to cooperate with Fourteenth Army in quick destruction of Polish forces in the area up to River Dunajec. The Fourteenth Army was to avoid the Katowice fortifications and instead break through Polish forces in the Krakow region and make for River Dunajec. The Eighth Army would protect Tenth Army’s northern flank and advance on Lodz.

Remnants of the Polish Army would then be destroyed in a pincer movement. Any large Polish forces still capable of putting up resistance would be prevented from escaping over the Vistula line and annihilated by two further offensives, one from the north and one from the south, which would be launched from behind the Vistula and its tributaries.

Role of the Luftwaffe was to destroy the Polish Air Force and its installations, to disrupt mobilization by attacking the recruitment centres and to prevent the concentration of troops by destroying the transport network. Parachute troops would also be held ready for giving immediate support where required. The Navy’s part was limited to keeping open the sea links with East Prussia and to blockading Gdynia and the Gulf of Danzig.

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