在日本全面侵华的过程中，1937年8月31日组建的华北方面军主要负责侵略华北。作为七七事变之后日本在中国设立的第一个“方面军”，也是日本在中国存续时间最长的“方面军”，华北方面军的侵略活动贯穿日本全面侵华战争的“始”与“终”。1937至1938年于中国而言是全面抗战时期的战略防御阶段，于日本而言则是全面侵华战争的战略进攻阶段。在这一时期，华北方面军相继实施了对察哈尔、山西、绥远、河北、山东和江苏等地的大规模侵略作战。

七七事变爆发之际，日本陆军中央虽曾一度确立“不扩大事件，现地解决”的事变处理方针，但该方针很快被持“对华一击论”的“扩大派”所推翻。而放弃“不扩大”方针的结果之一便是日本于全面侵华初期前后三次大规模向华北增派部队逾8个师团。后来，也正是这8个师团构成了华北方面军的基干部队。因而，日本在1937年8月31日之前向华北增兵的过程，某种程度上亦可被视为组建华北方面军的“缩影”。此外，为了华北方面军的侵略作战能够顺利开展，日本陆军中央在选择该方面军的相关指挥人员和部队时，均进行了针对性地安排。

七七事变爆发之后，日本关东军为实现此前未遂的“内蒙工作”，迅速出兵华北，联合日本的中国驻屯军等部侵占北平和天津。占领平津之后，日本陆军中央和中国驻屯军最初计划进攻平津地区以南的河北省。不过，后来为了保障中国驻屯军南下作战的侧背“安全”，日本陆军中央转而决定以第五师团和关东军先行实施“察哈尔作战”。此役过后，日本陆军中央和华北方面军一致希望将第五师团调往河北，察哈尔地区交由关东军警备，暂不进攻太原和绥远。与此相对，战场一线的第五师团和关东军却多次提议进攻太原。华北方面军虽起初不同意进攻太原，但由于日本陆军中央改变态度，下令实施这一“作战”，最后也不得不遵令执行。在进攻太原的过程中，第五师团一度被中国军队阻于忻口，后经华北方面军自正太铁路方面增兵才得以侵占太原。关东军则通过上述一系列“作战”，迅速在察南、晋北和绥远地区扶植了相应的傀儡政权。

日本陆军中央和中国驻屯军在侵占平津之前已计划沿着平汉线和津浦线侵略中国，华北方面军成立之后亦基本继承了这一作战计划。执行这一作战计划的第一军和第二军在进攻伊始，分别沿着平汉铁路和津浦铁路向南“作战”。不过，在随后进行的“涿州、保定会战”以及“石家庄会战”中，第一军虽还是沿着平汉铁路进攻，但第二军的进攻路线则改为一部继续沿着津浦铁路南侵，主力由津浦铁路推进至平汉铁路沿线，谋求与该方面的第一军合围中国军队。由于中国军队的快速撤退，华北方面军的这一作战企图并未实现。此外，以“围歼”中国军队主力为借口，华北方面军在侵略作战过程中多次突破日本陆军中央的“作战限定线”。在上述两次“会战”之后，华北方面军又欲实施“山东作战”。日本陆军中央虽基于先集中兵力侵占上海和南京的考虑，暂时限制了这一作战，但随着华中日军攻下南京，华北方面军的“山东作战”请求也随即得到批准。

1938年初，日本陆军中央暂时确定了同年8月之前不对中国发动新的大规模侵略作战的方针。然而，华北方面军却基于打通津浦铁路、围歼中国军队主力的目的，多次电请进攻徐州。在这一作战提议被日本陆军中央否决之后，第二军又转而提出为了击退正面的中国军队，希望实施“有限南进作战”。日本陆军中央虽一度认可第二军“有限南进作战”的请求，但前者却于台儿庄附近遭遇败北。由于这一败仗以及参谋本部内部的人事变动，日本陆军中央于1938年4月初决定提前开展徐州会战。此后，华北方面军虽在华中派遣军的配合下侵占徐州，但在作战过程中却出现较多问题：一是与华中派遣军关于徐州会战的作战目标和发起时间存在分歧；二是第一军在进攻徐州的过程中出现不遵守命令的情况；三是在陇海铁路沿线的侵略作战中，华北方面军再一次出现超出“作战限定线”的行动。

总而言之，华北方面军在1937至1938年的侵略作战行动表明，其虽接连侵占中国大片领土，但具体作战过程却也存在诸多问题。首先，华北方面军在1937至1938年期间围绕具体的侵略作战步骤却与各方存在着诸多歧异。其次，就具体的战略而言，华北方面军在实际作战过程中则存在许多误判乃至失误，比如将对华作战的重点置于平汉铁路沿线地区以及基于“短期决战”的思想，谋求“围歼”中国军队主力等。最后，华北方面军虽多数时候都能够遵循日本陆军中央的命令，但无论是其自身还是其隶下的一线部队都有许多“自主”行为。与此相对，中国军队在这一时期虽“屡战屡败”，但在具体抗战过程中也有诸多值得重新评价乃至肯定的方面。

During the comprehensive invasion of China by Japan, the North China Area Army, which was established on August 31, 1937, was primarily responsible for aggressions in North China. As the first "Area Army" established by Japan in China after the Marco Polo Bridge Incident, it also held the longest duration of presence among Japan's "Area Armies" in China. The aggressive activities of the North China Area Army spanned from the beginning to the end of Japan's comprehensive invasion of China. From 1937 to 1938, it marked the strategic defensive phase of the overall resistance war for China, while for Japan, it represented the strategic offensive phase of the comprehensive invasion of China. During this period, the North China Area Army successively conducted large-scale invasion operations in areas such as Chahar, Shanxi, Suiyuan, Hebei, Shandong, and Jiangsu.

At the outbreak of the Marco Polo Bridge Incident, although the Imperial Japanese Army General Staff initially established the policy of "not expanding the incident and resolving it locally," this policy was quickly overturned by the "Expansionists" advocating for a "one-strike theory" against China. One of the consequences of abandoning the "non-expansion" policy was Japan's dispatch of over 8 divisions to North China in three large-scale reinforcements during the early stages of the comprehensive invasion of China. These 8 divisions later formed the core forces of the North China Area Army. Therefore, the process of Japan's reinforcement of troops to North China before August 31, 1937 can also be seen as a "microcosm" of the establishment of the North China Area Army to some extent. Additionally, in order to ensure the smooth operations of the North China Area Army's aggression, the Imperial Japanese Army General Staff made targeted arrangements in selecting the relevant commanding officers and units for this theater of operations.

After the Marco Polo Bridge Incident, the Kwantung Army swiftly deployed to North China in order to achieve their previously unsuccessful "Inner Mongolia work," joining forces with the China Garrison Force and so on to occupy Beiping and Tianjin. Following the occupation of Beiping and Tianjin, the Imperial Japanese Army General Staff and the China Garrison Force initially planned to launch an attack on Hebei Province south of the occupied area. However, later on, in order to ensure the "security" of the rear flank for the southward operations of the China Garrison Force, the Imperial Japanese Army General Staff decided to carry out the "Chahar Operation" first with the 5th Division and the Kwantung Army. After this operation, both the Imperial Japanese Army General Staff and the North China Area Army desired to transfer the 5th Division to Hebei Province, leaving the Chahar region under the security of the Kwantung Army, temporarily refraining from attacking Taiyuan and Suiyuan. On the other hand, the frontline forces of the 5th Division and the Kwantung Army repeatedly proposed an attack on Taiyuan. Although the North China Area Army initially disagreed with the attack on Taiyuan, due to a change in attitude by the Imperial Japanese Army General Staff, the order was given to carry out this "operation," and ultimately they had to comply and execute it. During the process of attacking Taiyuan, the 5th Division was temporarily hindered by Chinese forces at Xinkou, but later managed to occupy Taiyuan with reinforcements from the North China Area Army via the Zhengtai Railway. Meanwhile, the Kwantung Army, through the aforementioned series of "operations," swiftly established corresponding puppet regimes in the southern part of Chahar, northern Shanxi, and Suiyuan regions.

The Imperial Japanese Army General Staff and the China Garrison Force had already planned to invade China along the Pinghan Railway and the Jinpu Railway before occupying Beiping and Tianjin. After the establishment of the North China Area Army, it essentially inherited this operational plan. The First Army and the Second Army, tasked with executing this plan, launched their offensives along the Pinghan Railway and the Jinpu Railway, respectively. However, in the subsequent "Zhuozhou-Baoding Campaign" and the "Shijiazhuang Campaign," while the First Army continued its advance along the Pinghan Railway, the Second Army's attack route shifted. A portion of the Second Army continued southward along the Jinpu Railway, with the main force advancing from the Jinpu Railway to the Pinghan Railway, aiming to encircle the Chinese forces in conjunction with the First Army. Due to the rapid retreat of the Chinese forces, the North China Area Army's attempt in this operation was not realized. Furthermore, under the pretext of "encircling" the main Chinese forces, the North China Area Army repeatedly broke through the operational limits set by the Imperial Japanese Army General Staff during the invasion campaign. After the aforementioned two "campaigns," the North China Area Army intended to carry out the "Shandong Operation." Although the Imperial Japanese Army General Staff temporarily restricted this operation due to the priority of concentrating forces to capture Shanghai and Nanjing, the approval for the North China Area Army's request for the "Shandong Operation" came immediately after the Central China Expeditionary Army captured Nanjing.

In early 1938, the Imperial Japanese Army General Staff temporarily decided on a policy not to launch new large-scale aggressive operations against China before August of that year. However, the North China Area Army, with the aim of opening up the Jinpu Railway and encircling the main Chinese forces, repeatedly requested to attack Xuzhou. After this operational proposal was rejected by the Imperial Japanese Army General Staff, the Second Army proposed a "Limited Southward Advance Operation" to repel the Chinese forces on the front line. Although the Imperial Japanese Army General Staff initially approved the Second Army's request for the "Limited Southward Advance Operation," the Second Army suffered a defeat near Tai'erzhuang. Due to this loss and changes in personnel within the General Staff, the Imperial Japanese Army Central Command decided in early April 1938 to advance the Xuzhou Campaign ahead of schedule. Subsequently, the North China Area Army, with the assistance of the Central China Expeditionary Army, occupied Xuzhou. However, several issues arose during the operation: first, there were differences between the North China Area Army and the Central China Expeditionary Army regarding the objectives and the timing of the Xuzhou Campaign; second, the First Army failed to follow orders during the attack on Xuzhou; and third, the North China Area Army once again exceeded the operational limits set by the General Staff in the aggressive operations along the Longhai Railway.

In conclusion, the aggressive military operations conducted by the North China Area Army from 1937 to 1938 demonstrated that while they successfully occupied significant territories in China, there were also numerous issues in the specific operational process. Firstly, during the period from 1937 to 1938, there were various disagreements among different parties regarding the specific steps of the aggressive operations conducted by the North China Area Army. Secondly, in terms of strategy, the North China Area Army made several misjudgments and mistakes during the actual combat process. For example, they focused their efforts on the areas along the Pinghan Railway and pursued the idea of a "short-term decisive battle" in an attempt to encircle the main Chinese forces. Lastly, although the North China Area Army mostly followed orders from the Imperial Japanese Army Central Command, both the army itself and its frontline units exhibited numerous instances of "autonomous" behavior. In contrast, despite experiencing repeated defeats during this period, the Chinese army also demonstrated many aspects worthy of reassessment and recognition in the course of the resistance against the Japanese aggression.